Trial Outcomes & Findings for Phase 2 Shigella Vaccine and Challenge (NCT NCT04242264)

Results Overview

Following study vaccination on Days 1 and 29, participants were admitted to an inpatient facility and challenged with Shigella sonnei strain 53G on Day 57. From challenge through Day 63, all stools passed by challenged participants were graded for consistency, all grade 3-5\* stools were visually assessed for gross blood, and all gross blood-containing stools were confirmed via hemoccult test. A blinded endpoint review committee of independent Shigella experts determined whether shigellosis occurred for each participant based on number, weight, consistency, and hemoccult-positive status of stools, along with the presence of additional enteric symptoms. \*Stool consistency was graded according to the following scale: 1 = Normal stool (best outcome); 2 = Soft stool; 3 = Loose stool; 4 = Watery stool; 5 = Rice water (worst outcome).

Recruitment status

COMPLETED

Study phase

PHASE2

Target enrollment

69 participants

Primary outcome timeframe

Day 57 through Day 63

Results posted on

2025-04-24

Participant Flow

Participants were healthy males and non-pregnant females, 18-49 years inclusive at the time of first vaccination, who met all eligibility criteria. They were recruited from the general population at the participating study sites. Participants were enrolled between 11Oct2022 and 09Jan2024.

Participant milestones

Participant milestones
Measure	WRSs2 + WRSs2 (10^6 Cfu) 10\^6 colony forming units (cfu) of WRSs2 administered orally as a 31 mL suspension on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57. WRSs2 is a live-attenuated S. sonnei vaccine candidate derived from the wild type S. sonnei "Moseley" strain. The lyophilized WRSs2 vaccine was manufactured under current good manufacturing practice (cGMP) at the Walter Reed Army Institute of Research (WRAIR) Pilot Bioproduction Facility (PBF). Lyophilized WRSs2 vaccine was reconstituted and suspended in 0.9% sterile normal saline prior to administration. Challenge strain 53G is a virulent S. sonnei strain initially isolated from a child with diarrhea in Tokyo. The lyophilized 53G was manufactured under cGMP at WRAIR PBF. Lyophilized 53G was reconstituted and suspended in 0.9% sterile normal saline prior to administration.	WRSs2 + WRSs2 (5x10^5 Cfu) 5x10\^5 colony forming units (cfu) of WRSs2 administered orally as a 31 mL suspension on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57. WRSs2 is a live-attenuated S. sonnei vaccine candidate derived from the wild type S. sonnei "Moseley" strain. The lyophilized WRSs2 vaccine was manufactured under current good manufacturing practice (cGMP) at the Walter Reed Army Institute of Research (WRAIR) Pilot Bioproduction Facility (PBF). Lyophilized WRSs2 vaccine was reconstituted and suspended in 0.9% sterile normal saline prior to administration. Challenge strain 53G is a virulent S. sonnei strain initially isolated from a child with diarrhea in Tokyo. The lyophilized 53G was manufactured under cGMP at WRAIR PBF. Lyophilized 53G was reconstituted and suspended in 0.9% sterile normal saline prior to administration.	Placebo + WRSs2 (10^6 Cfu) Placebo administered orally as a 31 mL solution on Day 1, 10\^6 colony forming units (cfu) of WRSs2 administered orally as a 31 mL suspension on Day 29, and challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57. WRSs2 is a live-attenuated S. sonnei vaccine candidate derived from the wild type S. sonnei "Moseley" strain. The lyophilized WRSs2 vaccine was manufactured under current good manufacturing practice (cGMP) at the Walter Reed Army Institute of Research (WRAIR) Pilot Bioproduction Facility (PBF). Lyophilized WRSs2 vaccine was reconstituted and suspended in 0.9% sterile normal saline prior to administration. Placebo is 0.9% sterile normal saline of United States Pharmacopeia (USP) grade. Challenge strain 53G is a virulent S. sonnei strain initially isolated from a child with diarrhea in Tokyo. The lyophilized 53G was manufactured under cGMP at WRAIR PBF. Lyophilized 53G was reconstituted and suspended in 0.9% sterile normal saline prior to administration.	Placebo + Placebo Placebo administered orally as a 31 mL solution on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57. Placebo is 0.9% sterile normal saline of United States Pharmacopeia (USP) grade. Challenge strain 53G is a virulent S. sonnei strain initially isolated from a child with diarrhea in Tokyo. The lyophilized 53G was manufactured under cGMP at WRAIR PBF. Lyophilized 53G was reconstituted and suspended in 0.9% sterile normal saline prior to administration.
Overall Study STARTED	22	26	23	37
Overall Study COMPLETED	19	24	22	36
Overall Study NOT COMPLETED	3	2	1	1

Reasons for withdrawal

Reasons for withdrawal
Measure	WRSs2 + WRSs2 (10^6 Cfu) 10\^6 colony forming units (cfu) of WRSs2 administered orally as a 31 mL suspension on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57. WRSs2 is a live-attenuated S. sonnei vaccine candidate derived from the wild type S. sonnei "Moseley" strain. The lyophilized WRSs2 vaccine was manufactured under current good manufacturing practice (cGMP) at the Walter Reed Army Institute of Research (WRAIR) Pilot Bioproduction Facility (PBF). Lyophilized WRSs2 vaccine was reconstituted and suspended in 0.9% sterile normal saline prior to administration. Challenge strain 53G is a virulent S. sonnei strain initially isolated from a child with diarrhea in Tokyo. The lyophilized 53G was manufactured under cGMP at WRAIR PBF. Lyophilized 53G was reconstituted and suspended in 0.9% sterile normal saline prior to administration.	WRSs2 + WRSs2 (5x10^5 Cfu) 5x10\^5 colony forming units (cfu) of WRSs2 administered orally as a 31 mL suspension on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57. WRSs2 is a live-attenuated S. sonnei vaccine candidate derived from the wild type S. sonnei "Moseley" strain. The lyophilized WRSs2 vaccine was manufactured under current good manufacturing practice (cGMP) at the Walter Reed Army Institute of Research (WRAIR) Pilot Bioproduction Facility (PBF). Lyophilized WRSs2 vaccine was reconstituted and suspended in 0.9% sterile normal saline prior to administration. Challenge strain 53G is a virulent S. sonnei strain initially isolated from a child with diarrhea in Tokyo. The lyophilized 53G was manufactured under cGMP at WRAIR PBF. Lyophilized 53G was reconstituted and suspended in 0.9% sterile normal saline prior to administration.	Placebo + WRSs2 (10^6 Cfu) Placebo administered orally as a 31 mL solution on Day 1, 10\^6 colony forming units (cfu) of WRSs2 administered orally as a 31 mL suspension on Day 29, and challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57. WRSs2 is a live-attenuated S. sonnei vaccine candidate derived from the wild type S. sonnei "Moseley" strain. The lyophilized WRSs2 vaccine was manufactured under current good manufacturing practice (cGMP) at the Walter Reed Army Institute of Research (WRAIR) Pilot Bioproduction Facility (PBF). Lyophilized WRSs2 vaccine was reconstituted and suspended in 0.9% sterile normal saline prior to administration. Placebo is 0.9% sterile normal saline of United States Pharmacopeia (USP) grade. Challenge strain 53G is a virulent S. sonnei strain initially isolated from a child with diarrhea in Tokyo. The lyophilized 53G was manufactured under cGMP at WRAIR PBF. Lyophilized 53G was reconstituted and suspended in 0.9% sterile normal saline prior to administration.	Placebo + Placebo Placebo administered orally as a 31 mL solution on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57. Placebo is 0.9% sterile normal saline of United States Pharmacopeia (USP) grade. Challenge strain 53G is a virulent S. sonnei strain initially isolated from a child with diarrhea in Tokyo. The lyophilized 53G was manufactured under cGMP at WRAIR PBF. Lyophilized 53G was reconstituted and suspended in 0.9% sterile normal saline prior to administration.
Overall Study Lost to Follow-up	2	2	1	1
Overall Study Withdrawal by Subject	1	0	0	0

Baseline Characteristics

Phase 2 Shigella Vaccine and Challenge

Baseline characteristics by cohort

Baseline characteristics by cohort
Measure	WRSs2 + WRSs2 (10^6 Cfu) n=22 Participants 10\^6 colony forming units (cfu) of WRSs2 administered orally as a 31 mL suspension on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	WRSs2 + WRSs2 (5x10^5 Cfu) n=26 Participants 5x10\^5 colony forming units (cfu) of WRSs2 administered orally as a 31 mL suspension on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + WRSs2 (10^6 Cfu) n=23 Participants Placebo administered orally as a 31 mL solution on Day 1, 10\^6 colony forming units (cfu) of WRSs2 administered orally as a 31 mL suspension on Day 29, and challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + Placebo n=37 Participants Placebo administered orally as a 31 mL solution on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Total n=108 Participants Total of all reporting groups
Age, Continuous	32 years STANDARD_DEVIATION 7.7 • n=5 Participants	31.8 years STANDARD_DEVIATION 7.5 • n=7 Participants	38.3 years STANDARD_DEVIATION 8.3 • n=5 Participants	31.2 years STANDARD_DEVIATION 7.8 • n=4 Participants	33 years STANDARD_DEVIATION 8.2 • n=21 Participants
Sex: Female, Male Female	13 Participants n=5 Participants	11 Participants n=7 Participants	12 Participants n=5 Participants	22 Participants n=4 Participants	58 Participants n=21 Participants
Sex: Female, Male Male	9 Participants n=5 Participants	15 Participants n=7 Participants	11 Participants n=5 Participants	15 Participants n=4 Participants	50 Participants n=21 Participants
Ethnicity (NIH/OMB) Hispanic or Latino	2 Participants n=5 Participants	2 Participants n=7 Participants	1 Participants n=5 Participants	4 Participants n=4 Participants	9 Participants n=21 Participants
Ethnicity (NIH/OMB) Not Hispanic or Latino	20 Participants n=5 Participants	24 Participants n=7 Participants	22 Participants n=5 Participants	33 Participants n=4 Participants	99 Participants n=21 Participants
Ethnicity (NIH/OMB) Unknown or Not Reported	0 Participants n=5 Participants	0 Participants n=7 Participants	0 Participants n=5 Participants	0 Participants n=4 Participants	0 Participants n=21 Participants
Race (NIH/OMB) American Indian or Alaska Native	0 Participants n=5 Participants	0 Participants n=7 Participants	0 Participants n=5 Participants	1 Participants n=4 Participants	1 Participants n=21 Participants
Race (NIH/OMB) Asian	0 Participants n=5 Participants	1 Participants n=7 Participants	0 Participants n=5 Participants	0 Participants n=4 Participants	1 Participants n=21 Participants
Race (NIH/OMB) Native Hawaiian or Other Pacific Islander	0 Participants n=5 Participants	0 Participants n=7 Participants	0 Participants n=5 Participants	0 Participants n=4 Participants	0 Participants n=21 Participants
Race (NIH/OMB) Black or African American	4 Participants n=5 Participants	6 Participants n=7 Participants	9 Participants n=5 Participants	14 Participants n=4 Participants	33 Participants n=21 Participants
Race (NIH/OMB) White	17 Participants n=5 Participants	18 Participants n=7 Participants	12 Participants n=5 Participants	18 Participants n=4 Participants	65 Participants n=21 Participants
Race (NIH/OMB) More than one race	0 Participants n=5 Participants	1 Participants n=7 Participants	2 Participants n=5 Participants	4 Participants n=4 Participants	7 Participants n=21 Participants
Race (NIH/OMB) Unknown or Not Reported	1 Participants n=5 Participants	0 Participants n=7 Participants	0 Participants n=5 Participants	0 Participants n=4 Participants	1 Participants n=21 Participants
Region of Enrollment United States	22 participants n=5 Participants	26 participants n=7 Participants	23 participants n=5 Participants	37 participants n=4 Participants	108 participants n=21 Participants
Body Mass Index	32.69 kg/m^2 STANDARD_DEVIATION 8.33 • n=5 Participants	28.29 kg/m^2 STANDARD_DEVIATION 5.17 • n=7 Participants	29.17 kg/m^2 STANDARD_DEVIATION 5.93 • n=5 Participants	29.72 kg/m^2 STANDARD_DEVIATION 6.89 • n=4 Participants	29.86 kg/m^2 STANDARD_DEVIATION 6.74 • n=21 Participants

PRIMARY outcome

Timeframe: Day 57 through Day 63

Population: The Full Analysis Population includes all randomized participants who were challenged with complete data for the primary efficacy endpoint. Participants will be analyzed according to the study arm to which they were randomized.

Following study vaccination on Days 1 and 29, participants were admitted to an inpatient facility and challenged with Shigella sonnei strain 53G on Day 57. From challenge through Day 63, all stools passed by challenged participants were graded for consistency, all grade 3-5\* stools were visually assessed for gross blood, and all gross blood-containing stools were confirmed via hemoccult test. A blinded endpoint review committee of independent Shigella experts determined whether shigellosis occurred for each participant based on number, weight, consistency, and hemoccult-positive status of stools, along with the presence of additional enteric symptoms. \*Stool consistency was graded according to the following scale: 1 = Normal stool (best outcome); 2 = Soft stool; 3 = Loose stool; 4 = Watery stool; 5 = Rice water (worst outcome).

Outcome measures

Outcome measures
Measure	WRSs2 + WRSs2 (10^6 Cfu or 5x10^5 Cfu) n=34 Participants 10\^6 colony forming units (cfu) or 5x10\^5 cfu of WRSs2 administered orally as a 31 mL suspension on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + Placebo n=26 Participants Placebo administered orally as a 31 mL solution on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + WRSs2 (10^6 Cfu) Placebo administered orally as a 31 mL solution on Day 1, 10\^6 colony forming units (cfu) of WRSs2 administered orally as a 31 mL suspension on Day 29, and challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + Placebo Placebo administered orally as a 31 mL solution on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.
The Proportion of Participants With Shigellosis Following Challenge With Shigella Sonnei 53G Through Day 63 in the Pooled Group of Participants Receiving Two Doses of 10^6 Cfu or 5x10^5 Cfu of WRSs2 Compared to Participants Receiving Two Doses of Placebo.	0.09 proportion of participants Interval 0.03 to 0.23	0.81 proportion of participants Interval 0.62 to 0.91	—	—

SECONDARY outcome

Timeframe: Day 57 through Day 65

Population: The Full Analysis Population includes all randomized participants who were challenged with complete data for the primary efficacy endpoint. Participants were analyzed according to the study arm to which they were randomized.

Following study vaccination on Days 1 and 29, participants were admitted to an inpatient facility and challenged with Shigella sonnei strain 53G on Day 57. From challenge through Day 63, all stools passed by challenged participants were graded for consistency, all grade 3-5\* stools were visually assessed for gross blood, and all gross blood-containing stools were confirmed via hemoccult test. A blinded endpoint review committee of independent Shigella experts determined whether shigellosis occurred for each participant based on number, weight, consistency, and hemoccult-positive status of stools, along with the presence of additional enteric symptoms. \*Stool consistency was graded according to the following scale: 1 = Normal stool (best outcome); 2 = Soft stool; 3 = Loose stool; 4 = Watery stool; 5 = Rice water (worst outcome).

Outcome measures

Outcome measures
Measure	WRSs2 + WRSs2 (10^6 Cfu or 5x10^5 Cfu) n=16 Participants 10\^6 colony forming units (cfu) or 5x10\^5 cfu of WRSs2 administered orally as a 31 mL suspension on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + Placebo n=18 Participants Placebo administered orally as a 31 mL solution on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + WRSs2 (10^6 Cfu) n=13 Participants Placebo administered orally as a 31 mL solution on Day 1, 10\^6 colony forming units (cfu) of WRSs2 administered orally as a 31 mL suspension on Day 29, and challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + Placebo n=26 Participants Placebo administered orally as a 31 mL solution on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.
The Proportion of Participants With Shigellosis Following Challenge With S. Sonnei 53G Through Day 63 in Participants Receiving 1 Dose of 10^6 Cfu, 2 Doses of 10^6 Cfu, or 2 Doses of 5x10^5 Cfu of WRSs2 Compared to Those Receiving Two Doses of Placebo.	0.19 proportion of participants Interval 0.07 to 0.43	0 proportion of participants Interval 0.0 to 0.18	0 proportion of participants Interval 0.0 to 0.23	0.81 proportion of participants Interval 0.62 to 0.91

SECONDARY outcome

Timeframe: Day 1 through Day 8, Day 29 through Day 36

Population: The Safety Population includes all participants who received at least one dose of study vaccination. The number of participants analyzed for solicited systemic AEs after each vaccination reflects the number of participants in the Safety Population who received the corresponding vaccination. Participants were analyzed according to the study product actually received, not necessarily the study product to which a participant was randomized.

Systemic solicited adverse events (AEs) were collected pre-vaccination, 90 minutes post-vaccination, and then daily for 7 days after each vaccination using a memory aid and graded on a scale of 0 (none), 1 (mild), 2 (moderate) and 3 (severe). Systemic events include fever, headache, arthralgia, nausea, pain/abdominal cramps, fatigue/malaise, myalgia, anorexia/loss of appetite, chills, vomiting, and diarrhea.

Outcome measures

Outcome measures
Measure	WRSs2 + WRSs2 (10^6 Cfu or 5x10^5 Cfu) n=22 Participants 10\^6 colony forming units (cfu) or 5x10\^5 cfu of WRSs2 administered orally as a 31 mL suspension on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + Placebo n=26 Participants Placebo administered orally as a 31 mL solution on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + WRSs2 (10^6 Cfu) n=22 Participants Placebo administered orally as a 31 mL solution on Day 1, 10\^6 colony forming units (cfu) of WRSs2 administered orally as a 31 mL suspension on Day 29, and challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + Placebo n=38 Participants Placebo administered orally as a 31 mL solution on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.
Number and Percentage of Participants With Solicited Systemic Adverse Events (AEs) Through 7 Days After Each Study Vaccination. Post second vaccination (Day 29 through Day 36)	13 Participants	17 Participants	11 Participants	22 Participants
Number and Percentage of Participants With Solicited Systemic Adverse Events (AEs) Through 7 Days After Each Study Vaccination. Post first vaccination (Day 1 through Day 8)	17 Participants	22 Participants	11 Participants	27 Participants

SECONDARY outcome

Timeframe: Day 1 through Day 57

Population: The Safety Population includes all participants who received at least one dose of study vaccination. Participants were analyzed according to the study product actually received, not necessarily the study product to which a participant was randomized.

ICH E6 defines an AE as any untoward medical occurrence in a patient or clinical investigation subject administered a pharmaceutical product regardless of its causal relationship to the study treatment. FDA defines an AE as any untoward medical occurrence associated with the use of a drug in humans, whether or not considered drug related. An AE can therefore be any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease temporally associated with the use of medicinal (investigational) product. The occurrence of an AE may come to the attention of study personnel during study visits and interviews of a study recipient presenting for medical care, or upon review by a study monitor. An AE is considered related if there is a reasonable possibility that the study product caused the AE. Reasonable possibility means that there is evidence to suggest a causal relationship between the study product and the AE.

Outcome measures

Outcome measures
Measure	WRSs2 + WRSs2 (10^6 Cfu or 5x10^5 Cfu) n=22 Participants 10\^6 colony forming units (cfu) or 5x10\^5 cfu of WRSs2 administered orally as a 31 mL suspension on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + Placebo n=26 Participants Placebo administered orally as a 31 mL solution on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + WRSs2 (10^6 Cfu) n=22 Participants Placebo administered orally as a 31 mL solution on Day 1, 10\^6 colony forming units (cfu) of WRSs2 administered orally as a 31 mL suspension on Day 29, and challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + Placebo n=38 Participants Placebo administered orally as a 31 mL solution on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.
Number and Percentage of Participants With Vaccine-related Unsolicited AEs Through 28 Days Post Last Vaccination	2 Participants	5 Participants	2 Participants	0 Participants

SECONDARY outcome

Timeframe: Day 1 through Day 180

Population: The Safety Population includes all participants who received at least one dose of study vaccination. Participants were analyzed according to the study product actually received, not necessarily the study product to which a participant was randomized.

An AE or suspected adverse reaction is considered "serious" if, in the view of either the investigator or sponsor, it results in any of the following outcomes: * Death * A life-threatening AE * Inpatient hospitalization or prolongation of existing hospitalization * A persistent or significant incapacity or substantial disruption of the ability to conduct normal life functions * A congenital anomaly/birth defect * Important medical events that may not result in death, be life-threatening, or require hospitalizations may be considered serious when, based upon appropriate medical judgment they may jeopardize the patient or subject and may require medical or surgical intervention to prevent one of the outcomes listed in this definition.

Outcome measures

Outcome measures
Measure	WRSs2 + WRSs2 (10^6 Cfu or 5x10^5 Cfu) n=22 Participants 10\^6 colony forming units (cfu) or 5x10\^5 cfu of WRSs2 administered orally as a 31 mL suspension on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + Placebo n=26 Participants Placebo administered orally as a 31 mL solution on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + WRSs2 (10^6 Cfu) n=22 Participants Placebo administered orally as a 31 mL solution on Day 1, 10\^6 colony forming units (cfu) of WRSs2 administered orally as a 31 mL suspension on Day 29, and challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + Placebo n=38 Participants Placebo administered orally as a 31 mL solution on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.
Number and Percentage of Participants With SAEs Through Study Day 180 or Until Resolution or Stabilization Even if This Extends Beyond the Study-reporting Period.	0 Participants	0 Participants	0 Participants	0 Participants

SECONDARY outcome

Timeframe: Day 15, Day 29, Day 43, and Day 56

Population: The Immunogenicity Population consists of all participants who received any study product and for whom immunogenicity endpoint data are available. Participants were analyzed according to the study product actually received, not necessarily the study product to which a participant was randomized.

Serum was collected pre-challenge at Day 1 (pre-dose 1), Day 15 (post-dose 1), Day 29 (pre-dose 2), Day 43 (post-dose 2), and Day 56 (post-dose 2) to assess IgG antibody response against LPS (a Shigella sonnei antigen) as measured by Enzyme Linked ImmunoSorbent Assay (ELISA). The number of participants with at least a 4-fold rise in antibody titer on each post-vaccination day as compared to pre-dose 1 is reported.

Outcome measures

Outcome measures
Measure	WRSs2 + WRSs2 (10^6 Cfu or 5x10^5 Cfu) n=22 Participants 10\^6 colony forming units (cfu) or 5x10\^5 cfu of WRSs2 administered orally as a 31 mL suspension on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + Placebo n=25 Participants Placebo administered orally as a 31 mL solution on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + WRSs2 (10^6 Cfu) n=22 Participants Placebo administered orally as a 31 mL solution on Day 1, 10\^6 colony forming units (cfu) of WRSs2 administered orally as a 31 mL suspension on Day 29, and challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + Placebo n=36 Participants Placebo administered orally as a 31 mL solution on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.
Number of Participants With >=4-fold Rise From Pre-vaccination in Anti-LPS (Lipopolysaccharide) IgG (Immunoglobulin G) Day 15 (Post-Dose 1)	16 Participants	19 Participants	0 Participants	0 Participants
Number of Participants With >=4-fold Rise From Pre-vaccination in Anti-LPS (Lipopolysaccharide) IgG (Immunoglobulin G) Day 29 (Pre-Dose 2)	13 Participants	12 Participants	0 Participants	0 Participants
Number of Participants With >=4-fold Rise From Pre-vaccination in Anti-LPS (Lipopolysaccharide) IgG (Immunoglobulin G) Day 43 (Post-Dose 2)	9 Participants	9 Participants	9 Participants	0 Participants
Number of Participants With >=4-fold Rise From Pre-vaccination in Anti-LPS (Lipopolysaccharide) IgG (Immunoglobulin G) Day 56 (Post-Dose 2)	8 Participants	7 Participants	7 Participants	0 Participants

SECONDARY outcome

Timeframe: Day 15, Day 29, Day 43, and Day 56

Population: The Immunogenicity Population consists of all participants who received any study product and for whom immunogenicity endpoint data are available. Participants were analyzed according to the study product actually received, not necessarily the study product to which a participant was randomized.

Serum was collected pre-challenge at Day 1 (pre-dose 1), Day 15 (post-dose 1), Day 29 (pre-dose 2), Day 43 (post-dose 2), and Day 56 (post-dose 2) to assess IgG antibody response against Invaplex (a Shigella sonnei antigen complex) as measured by Enzyme Linked ImmunoSorbent Assay (ELISA). The number of participants with at least a 4-fold rise in antibody titer on each post-vaccination day as compared to pre-dose 1 is reported.

Outcome measures

Outcome measures
Measure	WRSs2 + WRSs2 (10^6 Cfu or 5x10^5 Cfu) n=22 Participants 10\^6 colony forming units (cfu) or 5x10\^5 cfu of WRSs2 administered orally as a 31 mL suspension on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + Placebo n=25 Participants Placebo administered orally as a 31 mL solution on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + WRSs2 (10^6 Cfu) n=22 Participants Placebo administered orally as a 31 mL solution on Day 1, 10\^6 colony forming units (cfu) of WRSs2 administered orally as a 31 mL suspension on Day 29, and challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + Placebo n=36 Participants Placebo administered orally as a 31 mL solution on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.
Number of Participants With >=4-fold Rise From Pre-vaccination in Anti-Invaplex IgG (Immunoglobulin G) Day 15 (Post-Dose 1)	16 Participants	13 Participants	0 Participants	0 Participants
Number of Participants With >=4-fold Rise From Pre-vaccination in Anti-Invaplex IgG (Immunoglobulin G) Day 29 (Pre-Dose 2)	16 Participants	11 Participants	0 Participants	0 Participants
Number of Participants With >=4-fold Rise From Pre-vaccination in Anti-Invaplex IgG (Immunoglobulin G) Day 43 (Post-Dose 2)	14 Participants	10 Participants	9 Participants	1 Participants
Number of Participants With >=4-fold Rise From Pre-vaccination in Anti-Invaplex IgG (Immunoglobulin G) Day 56 (Post-Dose 2)	11 Participants	9 Participants	9 Participants	1 Participants

SECONDARY outcome

Timeframe: Day 15, Day 29, Day 43, and Day 56

Population: The Immunogenicity Population consists of all participants who received any study product and for whom immunogenicity endpoint data are available. Participants were analyzed according to the study product actually received, not necessarily the study product to which a participant was randomized.

Serum was collected pre-challenge at Day 1 (pre-dose 1), Day 15 (post-dose 1), Day 29 (pre-dose 2), Day 43 (post-dose 2), and Day 56 (post-dose 2) to assess IgA antibody response against LPS (a Shigella sonnei antigen) as measured by Enzyme Linked ImmunoSorbent Assay (ELISA). The number of participants with at least a 4-fold rise in antibody titer on each post-vaccination day as compared to pre-dose 1 is reported.

Outcome measures

Outcome measures
Measure	WRSs2 + WRSs2 (10^6 Cfu or 5x10^5 Cfu) n=22 Participants 10\^6 colony forming units (cfu) or 5x10\^5 cfu of WRSs2 administered orally as a 31 mL suspension on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + Placebo n=25 Participants Placebo administered orally as a 31 mL solution on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + WRSs2 (10^6 Cfu) n=22 Participants Placebo administered orally as a 31 mL solution on Day 1, 10\^6 colony forming units (cfu) of WRSs2 administered orally as a 31 mL suspension on Day 29, and challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + Placebo n=36 Participants Placebo administered orally as a 31 mL solution on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.
Number of Participants With >=4-fold Rise From Pre-vaccination in Anti-LPS (Lipopolysaccharide) IgA (Immunoglobulin A) Day 15 (Post-Dose 1)	19 Participants	24 Participants	0 Participants	0 Participants
Number of Participants With >=4-fold Rise From Pre-vaccination in Anti-LPS (Lipopolysaccharide) IgA (Immunoglobulin A) Day 29 (Pre-Dose 2)	12 Participants	18 Participants	0 Participants	1 Participants
Number of Participants With >=4-fold Rise From Pre-vaccination in Anti-LPS (Lipopolysaccharide) IgA (Immunoglobulin A) Day 43 (Post-Dose 2)	9 Participants	12 Participants	13 Participants	1 Participants
Number of Participants With >=4-fold Rise From Pre-vaccination in Anti-LPS (Lipopolysaccharide) IgA (Immunoglobulin A) Day 56 (Post-Dose 2)	6 Participants	6 Participants	10 Participants	0 Participants

SECONDARY outcome

Timeframe: Day 15, Day 29, Day 43, and Day 56

Population: The Immunogenicity Population consists of all participants who received any study product and for whom immunogenicity endpoint data are available. Participants were analyzed according to the study product actually received, not necessarily the study product to which a participant was randomized.

Serum was collected pre-challenge at Day 1 (pre-dose 1), Day 15 (post-dose 1), Day 29 (pre-dose 2), Day 43 (post-dose 2), and Day 56 (post-dose 2) to assess IgA antibody response against Invaplex (a Shigella sonnei antigen complex) as measured by Enzyme Linked ImmunoSorbent Assay (ELISA). The number of participants with at least a 4-fold rise in antibody titer on each post-vaccination day as compared to pre-dose 1 is reported.

Outcome measures

Outcome measures
Measure	WRSs2 + WRSs2 (10^6 Cfu or 5x10^5 Cfu) n=22 Participants 10\^6 colony forming units (cfu) or 5x10\^5 cfu of WRSs2 administered orally as a 31 mL suspension on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + Placebo n=25 Participants Placebo administered orally as a 31 mL solution on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + WRSs2 (10^6 Cfu) n=22 Participants Placebo administered orally as a 31 mL solution on Day 1, 10\^6 colony forming units (cfu) of WRSs2 administered orally as a 31 mL suspension on Day 29, and challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + Placebo n=36 Participants Placebo administered orally as a 31 mL solution on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.
Number of Participants With >=4-fold Rise From Pre-vaccination in Anti-Invaplex IgA (Immunoglobulin A) Day 15 (Post-Dose 1)	20 Participants	24 Participants	0 Participants	0 Participants
Number of Participants With >=4-fold Rise From Pre-vaccination in Anti-Invaplex IgA (Immunoglobulin A) Day 29 (Pre-Dose 2)	14 Participants	21 Participants	0 Participants	1 Participants
Number of Participants With >=4-fold Rise From Pre-vaccination in Anti-Invaplex IgA (Immunoglobulin A) Day 43 (Post-Dose 2)	16 Participants	15 Participants	13 Participants	3 Participants
Number of Participants With >=4-fold Rise From Pre-vaccination in Anti-Invaplex IgA (Immunoglobulin A) Day 56 (Post-Dose 2)	9 Participants	9 Participants	13 Participants	2 Participants

SECONDARY outcome

Timeframe: Day 15 through Day 56

Population: The Immunogenicity Population consists of all participants who received any study product and for whom immunogenicity endpoint data are available. Participants were analyzed according to the study product actually received, not necessarily the study product to which a participant was randomized.

Serum was collected post-vaccination and pre-challenge at Day 15 (post-dose 1), Day 29 (pre-dose 2), Day 43 (post-dose 2), and Day 56 (post-dose 2) to assess IgG and IgA antibody responses against LPS and Invaplex (Shigella sonnei antigens) as measured by Enzyme Linked ImmunoSorbent Assay (ELISA). The maximum titer per participant between first vaccination (Day 1) and challenge (Day 57) is summarized by study arm via geometric mean and 95% confidence interval.

Outcome measures

Outcome measures
Measure	WRSs2 + WRSs2 (10^6 Cfu or 5x10^5 Cfu) n=22 Participants 10\^6 colony forming units (cfu) or 5x10\^5 cfu of WRSs2 administered orally as a 31 mL suspension on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + Placebo n=25 Participants Placebo administered orally as a 31 mL solution on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + WRSs2 (10^6 Cfu) n=22 Participants Placebo administered orally as a 31 mL solution on Day 1, 10\^6 colony forming units (cfu) of WRSs2 administered orally as a 31 mL suspension on Day 29, and challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + Placebo n=36 Participants Placebo administered orally as a 31 mL solution on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.
Maximum Anti-LPS (Lipopolysaccharide) and Anti-Invaplex Serum IgG (Immunoglobulin G) and IgA (Immunoglobulin A) Titer Post-vaccination Through Day 56 Anti-LPS IgG	1758.6 titer Interval 1081.3 to 2860.1	1837.9 titer Interval 1206.2 to 2800.5	997.4 titer Interval 624.4 to 1593.2	423.8 titer Interval 323.2 to 555.7
Maximum Anti-LPS (Lipopolysaccharide) and Anti-Invaplex Serum IgG (Immunoglobulin G) and IgA (Immunoglobulin A) Titer Post-vaccination Through Day 56 Anti-Invaplex IgG	5467.2 titer Interval 3373.0 to 8861.6	5571.5 titer Interval 3924.5 to 7909.7	1873.0 titer Interval 1078.0 to 3254.4	1371.6 titer Interval 970.3 to 1938.8
Maximum Anti-LPS (Lipopolysaccharide) and Anti-Invaplex Serum IgG (Immunoglobulin G) and IgA (Immunoglobulin A) Titer Post-vaccination Through Day 56 Anti-LPS IgA	1062.3 titer Interval 593.6 to 1901.1	1026.7 titer Interval 710.4 to 1483.9	341.7 titer Interval 186.3 to 626.9	110.1 titer Interval 85.6 to 141.6
Maximum Anti-LPS (Lipopolysaccharide) and Anti-Invaplex Serum IgG (Immunoglobulin G) and IgA (Immunoglobulin A) Titer Post-vaccination Through Day 56 Anti-Invaplex IgA	1814.9 titer Interval 956.3 to 3444.3	1472.3 titer Interval 1005.5 to 2155.9	426.0 titer Interval 221.0 to 821.3	110.1 titer Interval 80.5 to 150.6

SECONDARY outcome

Timeframe: Day 15 through Day 56

Population: The Immunogenicity Population consists of all participants who received any study product and for whom immunogenicity endpoint data are available. Participants were analyzed according to the study product actually received, not necessarily the study product to which a participant was randomized.

Serum was collected post-vaccination and pre-challenge at Day 15 (post-dose 1), Day 29 (pre-dose 2), Day 43 (post-dose 2), and Day 56 (post-dose 2) to assess IgG and IgA antibody responses against LPS and Invaplex (Shigella sonnei antigens) as measured by Enzyme Linked ImmunoSorbent Assay (ELISA). The peak fold-rise is calculated per participant at the maximum titer value post-vaccination (and before challenge) compared to pre-vaccination and is summarized by study arm via geometric mean fold-rise and 95% confidence interval.

Outcome measures

Outcome measures
Measure	WRSs2 + WRSs2 (10^6 Cfu or 5x10^5 Cfu) n=22 Participants 10\^6 colony forming units (cfu) or 5x10\^5 cfu of WRSs2 administered orally as a 31 mL suspension on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + Placebo n=25 Participants Placebo administered orally as a 31 mL solution on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + WRSs2 (10^6 Cfu) n=22 Participants Placebo administered orally as a 31 mL solution on Day 1, 10\^6 colony forming units (cfu) of WRSs2 administered orally as a 31 mL suspension on Day 29, and challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + Placebo n=36 Participants Placebo administered orally as a 31 mL solution on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.
Peak Fold-rise From Pre-vaccination in Anti-LPS (Lipopolysaccharide) and Anti-Invaplex Serum IgG (Immunoglobulin G) and IgA (Immunoglobulin A) Titer Anti-LPS IgG	5.0 fold rise from pre-vaccination Interval 3.4 to 7.4	4.1 fold rise from pre-vaccination Interval 3.1 to 5.5	3.2 fold rise from pre-vaccination Interval 1.8 to 5.7	1.2 fold rise from pre-vaccination Interval 1.1 to 1.3
Peak Fold-rise From Pre-vaccination in Anti-LPS (Lipopolysaccharide) and Anti-Invaplex Serum IgG (Immunoglobulin G) and IgA (Immunoglobulin A) Titer Anti-Invaplex IgG	7.8 fold rise from pre-vaccination Interval 4.9 to 12.3	3.3 fold rise from pre-vaccination Interval 2.3 to 4.7	3.1 fold rise from pre-vaccination Interval 2.0 to 4.9	1.3 fold rise from pre-vaccination Interval 1.1 to 1.4
Peak Fold-rise From Pre-vaccination in Anti-LPS (Lipopolysaccharide) and Anti-Invaplex Serum IgG (Immunoglobulin G) and IgA (Immunoglobulin A) Titer Anti-LPS IgA	12.0 fold rise from pre-vaccination Interval 7.0 to 20.7	11.8 fold rise from pre-vaccination Interval 8.4 to 16.6	4.3 fold rise from pre-vaccination Interval 2.3 to 7.8	1.2 fold rise from pre-vaccination Interval 1.0 to 1.4
Peak Fold-rise From Pre-vaccination in Anti-LPS (Lipopolysaccharide) and Anti-Invaplex Serum IgG (Immunoglobulin G) and IgA (Immunoglobulin A) Titer Anti-Invaplex IgA	20.6 fold rise from pre-vaccination Interval 11.3 to 37.4	14.3 fold rise from pre-vaccination Interval 9.5 to 21.6	6.2 fold rise from pre-vaccination Interval 3.2 to 12.0	1.4 fold rise from pre-vaccination Interval 1.1 to 1.7

SECONDARY outcome

Timeframe: Day 64, Day 71, Day 85, and Day 113

Population: This analysis includes participants in the Immunogenicity Population who were challenged. The Immunogenicity Population consists of all participants who received any study product and for whom immunogenicity endpoint data are available. Participants were analyzed according to the study product actually received, not necessarily the study product to which a participant was randomized.

Serum was collected post-challenge at Days 64, 71, 85, and 113 to assess IgG antibody response against LPS (a Shigella sonnei antigen) as measured by Enzyme Linked ImmunoSorbent Assay (ELISA). The number of participants with at least a 4-fold rise in antibody titer on each post-challenge day as compared to pre-challenge is reported.

Outcome measures

Outcome measures
Measure	WRSs2 + WRSs2 (10^6 Cfu or 5x10^5 Cfu) n=16 Participants 10\^6 colony forming units (cfu) or 5x10\^5 cfu of WRSs2 administered orally as a 31 mL suspension on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + Placebo n=18 Participants Placebo administered orally as a 31 mL solution on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + WRSs2 (10^6 Cfu) n=13 Participants Placebo administered orally as a 31 mL solution on Day 1, 10\^6 colony forming units (cfu) of WRSs2 administered orally as a 31 mL suspension on Day 29, and challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + Placebo n=26 Participants Placebo administered orally as a 31 mL solution on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.
Number of Participants With >=4-fold Rise From Pre-challenge in Anti-LPS (Lipopolysaccharide) IgG (Immunoglobulin G) Day 64	1 Participants	0 Participants	0 Participants	3 Participants
Number of Participants With >=4-fold Rise From Pre-challenge in Anti-LPS (Lipopolysaccharide) IgG (Immunoglobulin G) Day 71	2 Participants	1 Participants	0 Participants	20 Participants
Number of Participants With >=4-fold Rise From Pre-challenge in Anti-LPS (Lipopolysaccharide) IgG (Immunoglobulin G) Day 85	1 Participants	1 Participants	0 Participants	16 Participants
Number of Participants With >=4-fold Rise From Pre-challenge in Anti-LPS (Lipopolysaccharide) IgG (Immunoglobulin G) Day 113	1 Participants	0 Participants	1 Participants	12 Participants

SECONDARY outcome

Timeframe: Day 64, Day 71, Day 85, and Day 113

Population: This analysis includes participants in the Immunogenicity Population who were challenged. The Immunogenicity Population consists of all participants who received any study product and for whom immunogenicity endpoint data are available. Participants were analyzed according to the study product actually received, not necessarily the study product to which a participant was randomized.

Serum was collected post-challenge at Days 64, 71, 85, and 113 to assess IgG antibody response against Invaplex (a Shigella sonnei antigen complex) as measured by Enzyme Linked ImmunoSorbent Assay (ELISA). The number of participants with at least a 4-fold rise in antibody titer on each post-challenge day as compared to pre-challenge is reported.

Outcome measures

Outcome measures
Measure	WRSs2 + WRSs2 (10^6 Cfu or 5x10^5 Cfu) n=16 Participants 10\^6 colony forming units (cfu) or 5x10\^5 cfu of WRSs2 administered orally as a 31 mL suspension on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + Placebo n=18 Participants Placebo administered orally as a 31 mL solution on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + WRSs2 (10^6 Cfu) n=13 Participants Placebo administered orally as a 31 mL solution on Day 1, 10\^6 colony forming units (cfu) of WRSs2 administered orally as a 31 mL suspension on Day 29, and challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + Placebo n=26 Participants Placebo administered orally as a 31 mL solution on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.
Number of Participants With >=4-fold Rise From Pre-challenge in Anti-Invaplex IgG (Immunoglobulin G) Day 64	1 Participants	0 Participants	0 Participants	4 Participants
Number of Participants With >=4-fold Rise From Pre-challenge in Anti-Invaplex IgG (Immunoglobulin G) Day 71	4 Participants	1 Participants	0 Participants	20 Participants
Number of Participants With >=4-fold Rise From Pre-challenge in Anti-Invaplex IgG (Immunoglobulin G) Day 85	1 Participants	0 Participants	0 Participants	15 Participants
Number of Participants With >=4-fold Rise From Pre-challenge in Anti-Invaplex IgG (Immunoglobulin G) Day 113	0 Participants	0 Participants	0 Participants	14 Participants

SECONDARY outcome

Timeframe: Day 64, Day 71, Day 85, and Day 113

Population: This analysis includes participants in the Immunogenicity Population who were challenged. The Immunogenicity Population consists of all participants who received any study product and for whom immunogenicity endpoint data are available. Participants were analyzed according to the study product actually received, not necessarily the study product to which a participant was randomized.

Serum was collected post-challenge at Days 64, 71, 85, and 113 to assess IgA antibody response against LPS (a Shigella sonnei antigen) as measured by Enzyme Linked ImmunoSorbent Assay (ELISA). The number of participants with at least a 4-fold rise in antibody titer on each post-challenge day as compared to pre-challenge is reported.

Outcome measures

Outcome measures
Measure	WRSs2 + WRSs2 (10^6 Cfu or 5x10^5 Cfu) n=16 Participants 10\^6 colony forming units (cfu) or 5x10\^5 cfu of WRSs2 administered orally as a 31 mL suspension on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + Placebo n=18 Participants Placebo administered orally as a 31 mL solution on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + WRSs2 (10^6 Cfu) n=13 Participants Placebo administered orally as a 31 mL solution on Day 1, 10\^6 colony forming units (cfu) of WRSs2 administered orally as a 31 mL suspension on Day 29, and challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + Placebo n=26 Participants Placebo administered orally as a 31 mL solution on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.
Number of Participants With >=4-fold Rise From Pre-challenge in Anti-LPS (Lipopolysaccharide) IgA (Immunoglobulin A) Day 64	2 Participants	0 Participants	1 Participants	13 Participants
Number of Participants With >=4-fold Rise From Pre-challenge in Anti-LPS (Lipopolysaccharide) IgA (Immunoglobulin A) Day 71	7 Participants	7 Participants	1 Participants	24 Participants
Number of Participants With >=4-fold Rise From Pre-challenge in Anti-LPS (Lipopolysaccharide) IgA (Immunoglobulin A) Day 85	1 Participants	2 Participants	0 Participants	17 Participants
Number of Participants With >=4-fold Rise From Pre-challenge in Anti-LPS (Lipopolysaccharide) IgA (Immunoglobulin A) Day 113	0 Participants	0 Participants	0 Participants	7 Participants

SECONDARY outcome

Timeframe: Day 64, Day 71, Day 85, and Day 113

Population: This analysis includes participants in the Immunogenicity Population who were challenged. The Immunogenicity Population consists of all participants who received any study product and for whom immunogenicity endpoint data are available. Participants were analyzed according to the study product actually received, not necessarily the study product to which a participant was randomized.

Serum was collected post-challenge at Days 64, 71, 85, and 113 to assess IgA antibody response against Invaplex (a Shigella sonnei antigen complex) as measured by Enzyme Linked ImmunoSorbent Assay (ELISA). The number of participants with at least a 4-fold rise in antibody titer on each post-challenge day as compared to pre-challenge is reported.

Outcome measures

Outcome measures
Measure	WRSs2 + WRSs2 (10^6 Cfu or 5x10^5 Cfu) n=16 Participants 10\^6 colony forming units (cfu) or 5x10\^5 cfu of WRSs2 administered orally as a 31 mL suspension on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + Placebo n=18 Participants Placebo administered orally as a 31 mL solution on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + WRSs2 (10^6 Cfu) n=13 Participants Placebo administered orally as a 31 mL solution on Day 1, 10\^6 colony forming units (cfu) of WRSs2 administered orally as a 31 mL suspension on Day 29, and challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + Placebo n=26 Participants Placebo administered orally as a 31 mL solution on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.
Number of Participants With >=4-fold Rise From Pre-challenge in Anti-Invaplex IgA (Immunoglobulin A) Day 64	3 Participants	0 Participants	0 Participants	13 Participants
Number of Participants With >=4-fold Rise From Pre-challenge in Anti-Invaplex IgA (Immunoglobulin A) Day 71	5 Participants	8 Participants	1 Participants	22 Participants
Number of Participants With >=4-fold Rise From Pre-challenge in Anti-Invaplex IgA (Immunoglobulin A) Day 85	3 Participants	3 Participants	0 Participants	22 Participants
Number of Participants With >=4-fold Rise From Pre-challenge in Anti-Invaplex IgA (Immunoglobulin A) Day 113	0 Participants	0 Participants	0 Participants	9 Participants

SECONDARY outcome

Timeframe: Day 64 through Day 113

Population: This analysis includes participants in the Immunogenicity Population who were challenged. The Immunogenicity Population consists of all participants who received any study product and for whom immunogenicity endpoint data are available. Participants were analyzed according to the study product actually received, not necessarily the study product to which a participant was randomized.

Serum was collected post-challenge at Days 64, 71, 85, and 113 to assess IgG and IgA antibody responses against LPS and Invaplex (Shigella sonnei antigens) as measured by Enzyme Linked ImmunoSorbent Assay (ELISA). The maximum titer per participant between challenge (Day 57) and Day 113 is summarized by study arm via geometric mean and 95% confidence interval.

Outcome measures

Outcome measures
Measure	WRSs2 + WRSs2 (10^6 Cfu or 5x10^5 Cfu) n=16 Participants 10\^6 colony forming units (cfu) or 5x10\^5 cfu of WRSs2 administered orally as a 31 mL suspension on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + Placebo n=18 Participants Placebo administered orally as a 31 mL solution on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + WRSs2 (10^6 Cfu) n=13 Participants Placebo administered orally as a 31 mL solution on Day 1, 10\^6 colony forming units (cfu) of WRSs2 administered orally as a 31 mL suspension on Day 29, and challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + Placebo n=26 Participants Placebo administered orally as a 31 mL solution on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.
Maximum Anti-LPS (Lipopolysaccharide) and Anti-Invaplex Serum IgG (Immunoglobulin G) and IgA (Immunoglobulin A) Titer Post-challenge Through Day 113 Anti-LPS IgG	1233.8 titer Interval 709.0 to 2147.1	1175.8 titer Interval 805.7 to 1715.9	843.8 titer Interval 528.9 to 1346.2	2145.3 titer Interval 1419.7 to 3241.5
Maximum Anti-LPS (Lipopolysaccharide) and Anti-Invaplex Serum IgG (Immunoglobulin G) and IgA (Immunoglobulin A) Titer Post-challenge Through Day 113 Anti-Invaplex IgG	4525.5 titer Interval 2245.5 to 9120.5	4887.8 titer Interval 3237.6 to 7379.2	1600.0 titer Interval 717.4 to 3568.2	6400.0 titer Interval 4273.9 to 9583.8
Maximum Anti-LPS (Lipopolysaccharide) and Anti-Invaplex Serum IgG (Immunoglobulin G) and IgA (Immunoglobulin A) Titer Post-challenge Through Day 113 Anti-LPS IgA	436.2 titer Interval 211.3 to 900.4	400.0 titer Interval 229.7 to 696.5	275.4 titer Interval 166.7 to 454.9	1044.4 titer Interval 697.0 to 1564.9
Maximum Anti-LPS (Lipopolysaccharide) and Anti-Invaplex Serum IgG (Immunoglobulin G) and IgA (Immunoglobulin A) Titer Post-challenge Through Day 113 Anti-Invaplex IgA	590.7 titer Interval 219.3 to 1591.0	565.7 titer Interval 301.8 to 1060.4	323.2 titer Interval 225.9 to 462.3	1557.9 titer Interval 929.8 to 2610.3

SECONDARY outcome

Timeframe: Day 64 through Day 113

Population: This analysis includes participants in the Immunogenicity Population who were challenged. The Immunogenicity Population consists of all participants who received any study product and for whom immunogenicity endpoint data are available. Participants were analyzed according to the study product actually received, not necessarily the study product to which a participant was randomized.

Serum was collected post-challenge at Days 64, 71, 85, and 113 to assess IgG and IgA antibody responses against LPS and Invaplex (Shigella sonnei antigens) as measured by Enzyme Linked ImmunoSorbent Assay (ELISA). The peak fold-rise is calculated per participant at the maximum titer value post-challenge compared to pre-challenge and is summarized by study arm via geometric mean fold-rise and 95% confidence interval.

Outcome measures

Outcome measures
Measure	WRSs2 + WRSs2 (10^6 Cfu or 5x10^5 Cfu) n=16 Participants 10\^6 colony forming units (cfu) or 5x10\^5 cfu of WRSs2 administered orally as a 31 mL suspension on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + Placebo n=18 Participants Placebo administered orally as a 31 mL solution on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + WRSs2 (10^6 Cfu) n=13 Participants Placebo administered orally as a 31 mL solution on Day 1, 10\^6 colony forming units (cfu) of WRSs2 administered orally as a 31 mL suspension on Day 29, and challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + Placebo n=26 Participants Placebo administered orally as a 31 mL solution on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.
Peak Fold-rise From Pre-challenge in Anti-LPS (Lipopolysaccharide) and Anti-Invaplex Serum IgG (Immunoglobulin G) and IgA (Immunoglobulin A) Titer Anti-LPS IgG	1.8 fold rise from pre-challenge Interval 1.3 to 2.6	1.2 fold rise from pre-challenge Interval 0.9 to 1.5	1.1 fold rise from pre-challenge Interval 0.8 to 1.6	6.1 fold rise from pre-challenge Interval 4.0 to 9.4
Peak Fold-rise From Pre-challenge in Anti-LPS (Lipopolysaccharide) and Anti-Invaplex Serum IgG (Immunoglobulin G) and IgA (Immunoglobulin A) Titer Anti-Invaplex IgG	1.9 fold rise from pre-challenge Interval 1.3 to 2.8	1.2 fold rise from pre-challenge Interval 0.9 to 1.5	1.0 fold rise from pre-challenge Interval 0.7 to 1.3	5.8 fold rise from pre-challenge Interval 3.7 to 9.0
Peak Fold-rise From Pre-challenge in Anti-LPS (Lipopolysaccharide) and Anti-Invaplex Serum IgG (Immunoglobulin G) and IgA (Immunoglobulin A) Titer Anti-LPS IgA	2.6 fold rise from pre-challenge Interval 1.5 to 4.4	2.2 fold rise from pre-challenge Interval 1.3 to 3.6	1.2 fold rise from pre-challenge Interval 0.7 to 2.0	12.9 fold rise from pre-challenge Interval 8.2 to 20.3
Peak Fold-rise From Pre-challenge in Anti-LPS (Lipopolysaccharide) and Anti-Invaplex Serum IgG (Immunoglobulin G) and IgA (Immunoglobulin A) Titer Anti-Invaplex IgA	2.5 fold rise from pre-challenge Interval 1.4 to 4.5	2.5 fold rise from pre-challenge Interval 1.4 to 4.5	0.8 fold rise from pre-challenge Interval 0.5 to 1.3	18.3 fold rise from pre-challenge Interval 10.6 to 31.5

SECONDARY outcome

Timeframe: Baseline (day of last culture prior to dose 1) through Day 56

Population: The Shedding Analysis Population consists of all participants who received any study product. Participants were analyzed according to the study product they actually received, not necessarily the study product to which a participant was randomized.

Stool samples collected at baseline and on Days 4, 8, 15, 29, 32, 36, 43, and 56 were cultured for shedding of Shigella sonnei. For this outcome measure, "baseline" is considered the last day at which culture results were available pre-vaccination (may be at screening visit or Day 1). In the event a subject was unable to produce a bulk stool, rectal swabs were collected for culture.

Outcome measures

Outcome measures
Measure	WRSs2 + WRSs2 (10^6 Cfu or 5x10^5 Cfu) n=22 Participants 10\^6 colony forming units (cfu) or 5x10\^5 cfu of WRSs2 administered orally as a 31 mL suspension on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + Placebo n=26 Participants Placebo administered orally as a 31 mL solution on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + WRSs2 (10^6 Cfu) n=22 Participants Placebo administered orally as a 31 mL solution on Day 1, 10\^6 colony forming units (cfu) of WRSs2 administered orally as a 31 mL suspension on Day 29, and challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + Placebo n=38 Participants Placebo administered orally as a 31 mL solution on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.
Number of Participants Shedding Vaccine Strain in Their Stool by Culture Prior to Challenge Baseline (Pre-Dose 1)	0 Participants	0 Participants	0 Participants	0 Participants
Number of Participants Shedding Vaccine Strain in Their Stool by Culture Prior to Challenge Day 4 (Post-Dose 1)	15 Participants	14 Participants	0 Participants	0 Participants
Number of Participants Shedding Vaccine Strain in Their Stool by Culture Prior to Challenge Day 8 (Post-Dose 1)	15 Participants	19 Participants	0 Participants	0 Participants
Number of Participants Shedding Vaccine Strain in Their Stool by Culture Prior to Challenge Day 15 (Post-Dose 1)	3 Participants	10 Participants	0 Participants	0 Participants
Number of Participants Shedding Vaccine Strain in Their Stool by Culture Prior to Challenge Day 29 (Pre-Dose 2)	4 Participants	6 Participants	0 Participants	0 Participants
Number of Participants Shedding Vaccine Strain in Their Stool by Culture Prior to Challenge Day 32 (Post-Dose 2)	7 Participants	5 Participants	9 Participants	0 Participants
Number of Participants Shedding Vaccine Strain in Their Stool by Culture Prior to Challenge Day 36 (Post-Dose 2)	3 Participants	4 Participants	9 Participants	0 Participants
Number of Participants Shedding Vaccine Strain in Their Stool by Culture Prior to Challenge Day 43 (Post-Dose 2)	2 Participants	1 Participants	6 Participants	1 Participants
Number of Participants Shedding Vaccine Strain in Their Stool by Culture Prior to Challenge Day 56 (Post-Dose 2)	0 Participants	2 Participants	4 Participants	0 Participants

SECONDARY outcome

Timeframe: Day 57 (post-challenge) through Day 65

Population: The Full Analysis Population includes all randomized participants who were challenged with complete data for the primary efficacy endpoint. Participants were analyzed according to the study arm to which they were randomized.

Stool samples collected on Day 57 (post-challenge) through Day 65 were cultured for shedding of Shigella sonnei strain 53G. In the event a subject was unable to produce a bulk stool, rectal swabs were collected for culture.

Outcome measures

Outcome measures
Measure	WRSs2 + WRSs2 (10^6 Cfu or 5x10^5 Cfu) n=16 Participants 10\^6 colony forming units (cfu) or 5x10\^5 cfu of WRSs2 administered orally as a 31 mL suspension on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + Placebo n=18 Participants Placebo administered orally as a 31 mL solution on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + WRSs2 (10^6 Cfu) n=13 Participants Placebo administered orally as a 31 mL solution on Day 1, 10\^6 colony forming units (cfu) of WRSs2 administered orally as a 31 mL suspension on Day 29, and challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + Placebo n=26 Participants Placebo administered orally as a 31 mL solution on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.
Number of Participants Shedding 53G in Their Stool by Culture Post-challenge Day 57	0 Participants	0 Participants	3 Participants	0 Participants
Number of Participants Shedding 53G in Their Stool by Culture Post-challenge Day 58	0 Participants	1 Participants	2 Participants	5 Participants
Number of Participants Shedding 53G in Their Stool by Culture Post-challenge Day 59	4 Participants	3 Participants	2 Participants	19 Participants
Number of Participants Shedding 53G in Their Stool by Culture Post-challenge Day 60	6 Participants	3 Participants	4 Participants	19 Participants
Number of Participants Shedding 53G in Their Stool by Culture Post-challenge Day 61	9 Participants	6 Participants	5 Participants	13 Participants
Number of Participants Shedding 53G in Their Stool by Culture Post-challenge Day 62	7 Participants	4 Participants	3 Participants	13 Participants
Number of Participants Shedding 53G in Their Stool by Culture Post-challenge Day 63	0 Participants	1 Participants	1 Participants	0 Participants
Number of Participants Shedding 53G in Their Stool by Culture Post-challenge Day 64	0 Participants	0 Participants	0 Participants	0 Participants
Number of Participants Shedding 53G in Their Stool by Culture Post-challenge Day 65	0 Participants	0 Participants	0 Participants	0 Participants

SECONDARY outcome

Timeframe: Day 1 (post-vaccination) through Day 56

Population: This analysis includes participants in the Shedding Analysis Population with detected Shigella shedding post vaccination and prior to challenge. The Shedding Analysis Population consists of all participants who received any study product. Participants were analyzed according to the study product they actually received, not necessarily the study product to which a participant was randomized.

Stool samples collected on Day 1 (post-vaccination) and on Days 4, 8, 15, 29, 32, 36, 43, and 56 were cultured for shedding of Shigella sonnei. In the event a subject was unable to produce a bulk stool, rectal swabs were collected for culture. The duration of shedding is evaluated from the day of the initial positive culture result to the day of the last positive qualitative or quantitative culture, regardless of intermittent negative results.

Outcome measures

Outcome measures
Measure	WRSs2 + WRSs2 (10^6 Cfu or 5x10^5 Cfu) n=14 Participants 10\^6 colony forming units (cfu) or 5x10\^5 cfu of WRSs2 administered orally as a 31 mL suspension on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + Placebo n=22 Participants Placebo administered orally as a 31 mL solution on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + WRSs2 (10^6 Cfu) n=11 Participants Placebo administered orally as a 31 mL solution on Day 1, 10\^6 colony forming units (cfu) of WRSs2 administered orally as a 31 mL suspension on Day 29, and challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + Placebo n=1 Participants Placebo administered orally as a 31 mL solution on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.
Mean Duration of Shedding Vaccine Strain Post-vaccination Through Day 56 by Culture.	21.9 days Standard Deviation 14.6	15.9 days Standard Deviation 15.0	13.3 days Standard Deviation 10.3	1.0 days Standard Deviation NA Only one participant experienced shedding, so standard deviation of shedding duration could not be calculated.

SECONDARY outcome

Timeframe: Day 57 (post-challenge) through Day 65

Population: This analysis includes participants in the Full Analysis Population with detected Shigella shedding post challenge. The Full Analysis Population includes all randomized participants who were challenged with complete data for the primary efficacy endpoint. Participants were analyzed according to the study arm to which they were randomized.

Stool samples collected on Day 57 (post-challenge) through Day 65 were cultured for shedding of Shigella sonnei strain 53G. In the event a subject was unable to produce a bulk stool, rectal swabs were collected for culture. The duration of shedding is evaluated from the day of the initial positive culture result to the day of the last positive qualitative or quantitative culture, regardless of intermittent negative results.

Outcome measures

Outcome measures
Measure	WRSs2 + WRSs2 (10^6 Cfu or 5x10^5 Cfu) n=10 Participants 10\^6 colony forming units (cfu) or 5x10\^5 cfu of WRSs2 administered orally as a 31 mL suspension on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + Placebo n=8 Participants Placebo administered orally as a 31 mL solution on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + WRSs2 (10^6 Cfu) n=8 Participants Placebo administered orally as a 31 mL solution on Day 1, 10\^6 colony forming units (cfu) of WRSs2 administered orally as a 31 mL suspension on Day 29, and challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.	Placebo + Placebo n=23 Participants Placebo administered orally as a 31 mL solution on Day 1 and Day 29, followed by challenge with 1.5x10\^3 cfu of wild type Shigella sonnei (S. sonnei) 53G administered orally as a 31 mL suspension on Day 57.
Mean Duration of Shedding 53G Post-challenge Through Day 65 by Culture.	2.6 days Standard Deviation 1.3	2.6 days Standard Deviation 1.2	2.5 days Standard Deviation 1.3	3.1 days Standard Deviation 1.3

Adverse Events

WRSs2 + WRSs2 (10^6 Cfu)

Serious events: 0 serious events

Other events: 21 other events

Deaths: 0 deaths

WRSs2 + WRSs2 (5x10^5 Cfu)

Serious events: 0 serious events

Other events: 25 other events

Deaths: 0 deaths

Placebo + WRSs2 (10^6 Cfu)

Serious events: 0 serious events

Other events: 19 other events

Deaths: 0 deaths

Placebo + Placebo

Serious events: 0 serious events

Other events: 36 other events

Deaths: 0 deaths

Serious adverse events

Adverse event data not reported

Other adverse events

Additional Information

Robert W Frenck, Jr, M.D.

Cincinnati Children's Hospital Medical Center

Phone: 513-636-4463

Email: [email protected]

Results disclosure agreements

Principal investigator is a sponsor employee
Publication restrictions are in place