Trial Outcomes & Findings for A Phase III, Double-blind Study to Assess Safety and Efficacy of an RSV Maternal Unadjuvanted Vaccine, in Pregnant Women and Infants Born to Vaccinated Mothers (NCT NCT04605159)

Last Updated: 2025-02-20

Results Overview

An RSV-associated LRTI of any severity was characterized by a history of cough OR difficulty in breathing, AND a blood oxygen saturation by pulse oximetry (SpO2) lower than (\<) 95%, OR respiratory rate increase AND a confirmed RSV infection. An RSV-associated severe LRTI met the case definition of RSV-LRTI AND was additionally characterized by a SpO2 \<93%, OR lower chest wall in-drawing, OR inability to feed, OR failure to respond/unconscious. Medically assessed = the infant was evaluated by a healthcare professional for the LRTI.

Recruitment status

TERMINATED

Study phase

PHASE3

Target enrollment

11194 participants

Primary outcome timeframe

From birth to Day 181 post-birth

Results posted on

2025-02-20

Participant Flow

A total of 11194 participants (5959 maternal participants and 5235 infants) completed the informed consent process, of which 5328 maternal participants were exposed to the study intervention, and 5235 infants were born to those exposed mothers (RSV MAT Group - Mother and Placebo Group - Mother). Therefore, 10563 participants started the study.

Participant milestones

Participant milestones
Measure	RSV MAT Group - Mother Maternal participants received a single dose of the RSV MAT vaccine administered at Day 1 in this study.	Placebo Group - Mother Maternal participants received a single dose of placebo administered at Day 1 in this study.	RSV MAT Group - Infant This group consisted of infants born to mothers (from RSV MAT Group - Mother) who received a single dose of RSV MAT vaccine during pregnancy.	Placebo Group - Infant This group consisted of infants born to mothers (from Placebo Group - Mother) who received a single dose of placebo during pregnancy.
Overall Study STARTED	3557	1771	3494	1741
Overall Study COMPLETED	3374	1657	3236	1583
Overall Study NOT COMPLETED	183	114	258	158

Reasons for withdrawal

Reasons for withdrawal
Measure	RSV MAT Group - Mother Maternal participants received a single dose of the RSV MAT vaccine administered at Day 1 in this study.	Placebo Group - Mother Maternal participants received a single dose of placebo administered at Day 1 in this study.	RSV MAT Group - Infant This group consisted of infants born to mothers (from RSV MAT Group - Mother) who received a single dose of RSV MAT vaccine during pregnancy.	Placebo Group - Infant This group consisted of infants born to mothers (from Placebo Group - Mother) who received a single dose of placebo during pregnancy.
Overall Study Adverse Event	6	3	21	4
Overall Study Lost to Follow-up	74	45	119	80
Overall Study Protocol Violation	4	5	2	0
Overall Study Withdrawal by Subject	66	37	68	50
Overall Study Migrated / moved from the study area	32	22	41	21
Overall Study Other	1	2	7	3

Baseline Characteristics

A Phase III, Double-blind Study to Assess Safety and Efficacy of an RSV Maternal Unadjuvanted Vaccine, in Pregnant Women and Infants Born to Vaccinated Mothers

Baseline characteristics by cohort

Baseline characteristics by cohort
Measure	RSV MAT Group - Mother n=3557 Participants Maternal participants received a single dose of the RSV MAT vaccine administered at Day 1 in this study.	Placebo Group - Mother n=1771 Participants Maternal participants received a single dose of placebo administered at Day 1 in this study.	RSV MAT Group - Infant n=3494 Participants This group consisted of infants born to mothers (from RSV MAT Group - Mother) who received a single dose of RSV MAT vaccine during pregnancy.	Placebo Group - Infant n=1741 Participants This group consisted of infants born to mothers (from Placebo Group - Mother) who received a single dose of placebo during pregnancy.	Total n=10563 Participants Total of all reporting groups
Age, Customized 0 to 1 years of age	0 Participants n=5 Participants	0 Participants n=7 Participants	3494 Participants n=5 Participants	1741 Participants n=4 Participants	5235 Participants n=21 Participants
Age, Customized 18 to 34 years of age	2866 Participants n=5 Participants	1408 Participants n=7 Participants	0 Participants n=5 Participants	0 Participants n=4 Participants	4274 Participants n=21 Participants
Age, Customized 35 to 39 years of age	581 Participants n=5 Participants	300 Participants n=7 Participants	0 Participants n=5 Participants	0 Participants n=4 Participants	881 Participants n=21 Participants
Age, Customized 40 to 49 years of age	110 Participants n=5 Participants	63 Participants n=7 Participants	0 Participants n=5 Participants	0 Participants n=4 Participants	173 Participants n=21 Participants
Sex/Gender, Customized Female	3557 Participants n=5 Participants	1771 Participants n=7 Participants	1739 Participants n=5 Participants	867 Participants n=4 Participants	7934 Participants n=21 Participants
Sex/Gender, Customized Male	0 Participants n=5 Participants	0 Participants n=7 Participants	1753 Participants n=5 Participants	873 Participants n=4 Participants	2626 Participants n=21 Participants
Sex/Gender, Customized Other, Unspecified	0 Participants n=5 Participants	0 Participants n=7 Participants	2 Participants n=5 Participants	1 Participants n=4 Participants	3 Participants n=21 Participants
Race/Ethnicity, Customized ASIAN	663 Participants n=5 Participants	326 Participants n=7 Participants	641 Participants n=5 Participants	321 Participants n=4 Participants	1951 Participants n=21 Participants
Race/Ethnicity, Customized BLACK OR AFRICAN AMERICAN	517 Participants n=5 Participants	251 Participants n=7 Participants	463 Participants n=5 Participants	234 Participants n=4 Participants	1465 Participants n=21 Participants
Race/Ethnicity, Customized WHITE	1669 Participants n=5 Participants	838 Participants n=7 Participants	1634 Participants n=5 Participants	816 Participants n=4 Participants	4957 Participants n=21 Participants
Race/Ethnicity, Customized OTHER, UNSPECIFIED	685 Participants n=5 Participants	345 Participants n=7 Participants	730 Participants n=5 Participants	348 Participants n=4 Participants	2108 Participants n=21 Participants
Race/Ethnicity, Customized OTHER, DEIDENTIFIED	23 Participants n=5 Participants	11 Participants n=7 Participants	26 Participants n=5 Participants	22 Participants n=4 Participants	82 Participants n=21 Participants

PRIMARY outcome

Timeframe: From birth to Day 181 post-birth

Population: The analysis was performed on the Modified Full Analysis - Efficacy set for infants, which included all infant participants in the Exposed set who were born after at least 4 weeks of their maternal participants vaccination.

Outcome measures

Outcome measures
Measure	RSV MAT Group - Infant n=3426 Participants This group consisted of infants born to mothers (from RSV MAT Group - Mother) who received a single dose of RSV MAT vaccine during pregnancy.	Placebo Group - Infant n=1711 Participants This group consisted of infants born to mothers (from Placebo Group - Mother) who received a single dose of placebo during pregnancy.
Number of Infant Participants With Medically Assessed, RSV-associated Lower Respiratory Tract Illnesses (LRTIs) of Any Severity and RSV-associated Severe LRTIs From Birth to Day 181 Post-birth RSV-associated LRTIs of any severity	16 Participants	24 Participants
Number of Infant Participants With Medically Assessed, RSV-associated Lower Respiratory Tract Illnesses (LRTIs) of Any Severity and RSV-associated Severe LRTIs From Birth to Day 181 Post-birth RSV-associated severe LRTIs	8 Participants	14 Participants

PRIMARY outcome

Timeframe: From birth to Day 181 post-birth

Population: The analysis was performed on the Exposed Set for infants, which included the infants live-born to exposed maternal participants, whose parents/legally acceptable representative(s) (LARs) completed the informed consent process and signed the informed consent form.

An SAE is defined as any untoward medical occurrence that resulted in death, was life-threatening, required hospitalization or prolongation of existing hospitalization, resulted in disability/incapacity, was a congenital anomaly/birth defect or resulted in other situations that were considered serious per medical or scientific judgment. At least one SAE = occurrence of at least one SAE regardless of intensity grade or relation to vaccination.

Outcome measures

Outcome measures
Measure	RSV MAT Group - Infant n=3494 Participants This group consisted of infants born to mothers (from RSV MAT Group - Mother) who received a single dose of RSV MAT vaccine during pregnancy.	Placebo Group - Infant n=1741 Participants This group consisted of infants born to mothers (from Placebo Group - Mother) who received a single dose of placebo during pregnancy.
Number of Infant Participants With at Least One Serious Adverse Event (SAE) From Birth to Day 181 Post-birth	640 Participants	323 Participants

PRIMARY outcome

Timeframe: From birth to Day 181 post-birth

A participant was considered a 'withdrawal' from the study when no study procedure has occurred, no follow-up has been performed and no further information has been collected for this participant from the date of withdrawal/last contact. Participants who were withdrawn from the study because of AEs were clearly distinguished from participants who were withdrawn for other reasons. Investigators followed participants who were withdrawn from the study as a result of an AE until the event was resolved. At least one AE leading to study withdrawal = occurrence of at least one AE leading to study withdrawal regardless of intensity grade or relation to vaccination.

Outcome measures

Outcome measures
Measure	RSV MAT Group - Infant n=3494 Participants This group consisted of infants born to mothers (from RSV MAT Group - Mother) who received a single dose of RSV MAT vaccine during pregnancy.	Placebo Group - Infant n=1741 Participants This group consisted of infants born to mothers (from Placebo Group - Mother) who received a single dose of placebo during pregnancy.
Number of Infant Participants With at Least One Adverse Event (AE) Leading to Study Withdrawal From Birth to Day 181 Post-birth	19 Participants	4 Participants

PRIMARY outcome

Timeframe: From birth to Day 181 post-birth

An MAE is defined as an unsolicited AE, such as a symptom or illness, which required hospitalization, or emergency room visit, or visit to/by a health care provider. At least one MAE = occurrence of at least one MAE regardless of intensity grade or relation to vaccination.

Outcome measures

Outcome measures
Measure	RSV MAT Group - Infant n=3494 Participants This group consisted of infants born to mothers (from RSV MAT Group - Mother) who received a single dose of RSV MAT vaccine during pregnancy.	Placebo Group - Infant n=1741 Participants This group consisted of infants born to mothers (from Placebo Group - Mother) who received a single dose of placebo during pregnancy.
Number of Infant Participants With at Least One Medically Attended AE (MAE) From Birth to Day 181 Post-birth	2321 Participants	1135 Participants

PRIMARY outcome

Timeframe: From birth to Day 366 post-birth

Population: The analysis was performed on the Exposed Set for infants, which included the infants live-born to exposed maternal participants, whose parents/LARs completed the informed consent process and signed the informed consent form.

Outcome measures

Outcome measures
Measure	RSV MAT Group - Infant n=3494 Participants This group consisted of infants born to mothers (from RSV MAT Group - Mother) who received a single dose of RSV MAT vaccine during pregnancy.	Placebo Group - Infant n=1741 Participants This group consisted of infants born to mothers (from Placebo Group - Mother) who received a single dose of placebo during pregnancy.
Number of Infant Participants With at Least One SAE From Birth to Day 366 Post-birth	731 Participants	371 Participants

PRIMARY outcome

Timeframe: From birth to Day 366 post-birth

Outcome measures

Outcome measures
Measure	RSV MAT Group - Infant n=3494 Participants This group consisted of infants born to mothers (from RSV MAT Group - Mother) who received a single dose of RSV MAT vaccine during pregnancy.	Placebo Group - Infant n=1741 Participants This group consisted of infants born to mothers (from Placebo Group - Mother) who received a single dose of placebo during pregnancy.
Number of Infant Participants With at Least One AE Leading to Study Withdrawal From Birth to Day 366 Post-birth	21 Participants	4 Participants

PRIMARY outcome

Timeframe: From birth to Day 366 post-birth

Outcome measures

Outcome measures
Measure	RSV MAT Group - Infant n=3494 Participants This group consisted of infants born to mothers (from RSV MAT Group - Mother) who received a single dose of RSV MAT vaccine during pregnancy.	Placebo Group - Infant n=1741 Participants This group consisted of infants born to mothers (from Placebo Group - Mother) who received a single dose of placebo during pregnancy.
Number of Infant Participants With at Least One MAE From Birth to Day 366 Post-birth	2706 Participants	1330 Participants

SECONDARY outcome

Timeframe: From birth to Day 181 post-birth

Population: The analysis was performed on the Modified Full Analysis - Efficacy set for infants, which included all infant participants in the Exposed Set who were born after at least 4 weeks of their maternal participants vaccination.

RSV-associated hospitalization is defined as a confirmed RSV infection and hospitalized for acute medical condition. Hospitalization is defined as admission for observation or treatment based on the judgment of a health care provider.

Outcome measures

Outcome measures
Measure	RSV MAT Group - Infant n=3426 Participants This group consisted of infants born to mothers (from RSV MAT Group - Mother) who received a single dose of RSV MAT vaccine during pregnancy.	Placebo Group - Infant n=1711 Participants This group consisted of infants born to mothers (from Placebo Group - Mother) who received a single dose of placebo during pregnancy.
Number of Infant Participants With RSV-associated Hospitalizations From Birth to Day 181 Post-birth	14 Participants	14 Participants

SECONDARY outcome

Timeframe: From birth to Day 181 post-birth

Population: The analysis was performed on the Modified Full Analysis - Efficacy set for infants, which included all the infant participants in the Exposed Set who were born after at least 4 weeks of their maternal participants vaccination.

All-cause LRTI was characterized by history of cough OR difficulty in breathing, AND SpO2 \< 95%, OR respiratory rate increase.

Outcome measures

Outcome measures
Measure	RSV MAT Group - Infant n=3426 Participants This group consisted of infants born to mothers (from RSV MAT Group - Mother) who received a single dose of RSV MAT vaccine during pregnancy.	Placebo Group - Infant n=1711 Participants This group consisted of infants born to mothers (from Placebo Group - Mother) who received a single dose of placebo during pregnancy.
Number of Infant Participants With All-cause LRTIs From Birth to Day 181 Post-birth	162 Participants	103 Participants

SECONDARY outcome

Timeframe: From birth to Day 181 post-birth

All-cause LRTI was characterized by history of cough OR difficulty in breathing, AND SpO2 \< 95%, OR respiratory rate increase. Hospitalization is defined as admission for observation or treatment based on the judgment of a health care provider.

Outcome measures

Outcome measures
Measure	RSV MAT Group - Infant n=3426 Participants This group consisted of infants born to mothers (from RSV MAT Group - Mother) who received a single dose of RSV MAT vaccine during pregnancy.	Placebo Group - Infant n=1711 Participants This group consisted of infants born to mothers (from Placebo Group - Mother) who received a single dose of placebo during pregnancy.
Number of Infant Participants With All-cause LRTIs With Hospitalization From Birth to Day 181 Post-birth	30 Participants	22 Participants

SECONDARY outcome

Timeframe: From birth to Day 366 post-birth

An RSV-associated LRTI of any severity was characterized by a history of cough OR difficulty in breathing, AND an SpO2 \<95%, OR respiratory rate increase AND a confirmed RSV infection. An RSV-associated severe LRTI met the case definition of RSV-LRTI AND was additionally characterized by an SpO2 \<93%, OR lower chest wall in-drawing, OR inability to feed, OR failure to respond/unconscious. Medically assessed = the infant was evaluated by a healthcare professional for the LRTI.

Outcome measures

Outcome measures
Measure	RSV MAT Group - Infant n=3426 Participants This group consisted of infants born to mothers (from RSV MAT Group - Mother) who received a single dose of RSV MAT vaccine during pregnancy.	Placebo Group - Infant n=1711 Participants This group consisted of infants born to mothers (from Placebo Group - Mother) who received a single dose of placebo during pregnancy.
Number of Infant Participants With Medically Assessed, RSV-associated Severe LRTIs From Birth to Day 366 Post-birth	38 Participants	22 Participants

SECONDARY outcome

Timeframe: From birth to Day 366 post-birth

Outcome measures

Outcome measures
Measure	RSV MAT Group - Infant n=3426 Participants This group consisted of infants born to mothers (from RSV MAT Group - Mother) who received a single dose of RSV MAT vaccine during pregnancy.	Placebo Group - Infant n=1711 Participants This group consisted of infants born to mothers (from Placebo Group - Mother) who received a single dose of placebo during pregnancy.
Number of Infant Participants With Medically Assessed, RSV-associated LRTIs of Any Severity From Birth to Day 366 Post-birth	67 Participants	43 Participants

SECONDARY outcome

Timeframe: From birth to Day 181 post-birth

Population: The analysis was performed on the Modified Full Analysis - Efficacy set for infants which included all the infant participants in the Exposed Set who were born after at least 4 weeks of their maternal participants vaccination.

Outcome measures

Outcome measures
Measure	RSV MAT Group - Infant n=3426 Participants This group consisted of infants born to mothers (from RSV MAT Group - Mother) who received a single dose of RSV MAT vaccine during pregnancy.	Placebo Group - Infant n=1711 Participants This group consisted of infants born to mothers (from Placebo Group - Mother) who received a single dose of placebo during pregnancy.
Number of Infant Participants With Medically Assessed, RSV-associated Severe LRTIs for RSV Subtype A and RSV Subtype B Separately From Birth to Day 181 Post-birth RSV A	2 Participants	3 Participants
Number of Infant Participants With Medically Assessed, RSV-associated Severe LRTIs for RSV Subtype A and RSV Subtype B Separately From Birth to Day 181 Post-birth RSV B	6 Participants	11 Participants

SECONDARY outcome

Timeframe: From birth to Day 181 post-birth

An RSV-associated LRTI of any severity was characterized by a history of cough OR difficulty in breathing, AND an SpO2 \<95%, OR respiratory rate increase AND a confirmed RSV infection. Medically assessed = the infant was evaluated by a healthcare professional for the LRTI. The RSV subtypes assessed for this analysis were RSV subtype A and RSV subtype B.

Outcome measures

Outcome measures
Measure	RSV MAT Group - Infant n=3426 Participants This group consisted of infants born to mothers (from RSV MAT Group - Mother) who received a single dose of RSV MAT vaccine during pregnancy.	Placebo Group - Infant n=1711 Participants This group consisted of infants born to mothers (from Placebo Group - Mother) who received a single dose of placebo during pregnancy.
Number of Infant Participants With Medically Assessed, RSV-associated LRTIs of Any Severity for RSV Subtype A and RSV Subtype B Separately From Birth to Day 181 Post-birth RSV A	6 Participants	8 Participants
Number of Infant Participants With Medically Assessed, RSV-associated LRTIs of Any Severity for RSV Subtype A and RSV Subtype B Separately From Birth to Day 181 Post-birth RSV B	10 Participants	16 Participants

SECONDARY outcome

Timeframe: From birth to Day 121 post-birth

Outcome measures

Outcome measures
Measure	RSV MAT Group - Infant n=3426 Participants This group consisted of infants born to mothers (from RSV MAT Group - Mother) who received a single dose of RSV MAT vaccine during pregnancy.	Placebo Group - Infant n=1711 Participants This group consisted of infants born to mothers (from Placebo Group - Mother) who received a single dose of placebo during pregnancy.
Number of Infant Participants With Medically Assessed, RSV-associated Severe LRTIs From Birth to Day 121 Post-birth	6 Participants	9 Participants

SECONDARY outcome

Timeframe: From birth to Day 121 post-birth

Outcome measures

Outcome measures
Measure	RSV MAT Group - Infant n=3426 Participants This group consisted of infants born to mothers (from RSV MAT Group - Mother) who received a single dose of RSV MAT vaccine during pregnancy.	Placebo Group - Infant n=1711 Participants This group consisted of infants born to mothers (from Placebo Group - Mother) who received a single dose of placebo during pregnancy.
Number of Infant Participants With Medically Assessed, RSV-associated LRTIs of Any Severity From Birth to Day 121 Post-birth	9 Participants	15 Participants

SECONDARY outcome

Timeframe: From birth to Day 181 post-birth

The number of infant participants with all-cause pneumonia is presented in this outcome measure.

Outcome measures

Outcome measures
Measure	RSV MAT Group - Infant n=3426 Participants This group consisted of infants born to mothers (from RSV MAT Group - Mother) who received a single dose of RSV MAT vaccine during pregnancy.	Placebo Group - Infant n=1711 Participants This group consisted of infants born to mothers (from Placebo Group - Mother) who received a single dose of placebo during pregnancy.
Number of Infant Participants With All-cause Pneumonia From Birth to Day 181 Post-birth	36 Participants	17 Participants

SECONDARY outcome

Timeframe: From birth to Day 366 post-birth

Outcome measures

Outcome measures
Measure	RSV MAT Group - Infant n=3426 Participants This group consisted of infants born to mothers (from RSV MAT Group - Mother) who received a single dose of RSV MAT vaccine during pregnancy.	Placebo Group - Infant n=1711 Participants This group consisted of infants born to mothers (from Placebo Group - Mother) who received a single dose of placebo during pregnancy.
Number of Infant Participants With RSV-associated Hospitalizations From Birth to Day 366 Post-birth	41 Participants	26 Participants

SECONDARY outcome

Timeframe: From study intervention administration (Day 1) to Day 181 post-delivery

Population: The analysis was performed on the Exposed Set for maternal participants, which included all maternal participants who received the study intervention.

RSV-associated MA-RTI is defined as a medically attended visit for RTI symptoms and confirmed RSV infection.

Outcome measures

Outcome measures
Measure	RSV MAT Group - Infant n=3557 Participants This group consisted of infants born to mothers (from RSV MAT Group - Mother) who received a single dose of RSV MAT vaccine during pregnancy.	Placebo Group - Infant n=1771 Participants This group consisted of infants born to mothers (from Placebo Group - Mother) who received a single dose of placebo during pregnancy.
Number of Maternal Participants With RSV-associated Medically Attended RTIs (RSV-MA-RTIs) From Study Intervention Administration (Day 1) to Day 181 Post-delivery	3 Participants	6 Participants

SECONDARY outcome

Timeframe: At Day 1 (before study intervention administration), at Day 31 and at delivery

Population: The analysis was performed on the Per Protocol - Immunogenicity set for maternal participants, which included all maternal participants who received the study intervention to which they were randomized and had post-vaccination immunogenicity data available for the specified analysis at each of the specified time points (i.e. Day 1, Day 31, delivery) minus those participants with protocol deviations that led to exclusion.

RSV-A neutralizing titers were determined by neutralization assay and expressed as geometric mean titers (GMTs).

Outcome measures

Outcome measures
Measure	RSV MAT Group - Infant n=404 Participants This group consisted of infants born to mothers (from RSV MAT Group - Mother) who received a single dose of RSV MAT vaccine during pregnancy.	Placebo Group - Infant n=196 Participants This group consisted of infants born to mothers (from Placebo Group - Mother) who received a single dose of placebo during pregnancy.
RSV-A Neutralizing Antibody Titers for Maternal Participants at Day 1, at Day 31 and at Delivery Day 1	637.2 Titers Interval 589.4 to 688.8	594.9 Titers Interval 527.3 to 671.2
RSV-A Neutralizing Antibody Titers for Maternal Participants at Day 1, at Day 31 and at Delivery Day 31	9196.9 Titers Interval 8310.8 to 10177.6	673.5 Titers Interval 578.8 to 783.7
RSV-A Neutralizing Antibody Titers for Maternal Participants at Day 1, at Day 31 and at Delivery Delivery	5703.1 Titers Interval 5196.3 to 6259.3	657.7 Titers Interval 575.4 to 751.8

SECONDARY outcome

Timeframe: At delivery or within 72 hours after birth

Population: The analysis was performed on the Per Protocol - Immunogenicity set for infants, which included all infant participants in the Exposed set who had post-delivery/birth immunogenicity data available for the specified analysis at the specified time points (i.e. at delivery or within 72 hours after birth), minus those who (a) were born less than 4 weeks post- maternal participant vaccination and/ or (b) had protocol deviations that led to exclusion.

RSV-A neutralizing titers were determined by neutralization assay and expressed as GMTs. The titers were measured on the cord blood sample collected at delivery, or on a blood sample collected from the infant within 72 hours after birth (if no cord blood sample could be obtained).

Outcome measures

Outcome measures
Measure	RSV MAT Group - Infant n=197 Participants This group consisted of infants born to mothers (from RSV MAT Group - Mother) who received a single dose of RSV MAT vaccine during pregnancy.	Placebo Group - Infant n=82 Participants This group consisted of infants born to mothers (from Placebo Group - Mother) who received a single dose of placebo during pregnancy.
RSV-A Neutralizing Antibody Titers for Infant Participants at Delivery or Within 72 Hours After Birth	9466.2 Titers Interval 8398.6 to 10669.5	725.9 Titers Interval 593.1 to 888.5

SECONDARY outcome

Timeframe: At Day 43 post-birth

Population: The analysis was performed on a sub-cohort from the Per Protocol - Immunogenicity set for infants, which included the infant participants for whom blood samples were collected for the specified analysis at Day 43 post-birth.

RSV-A neutralizing titers were determined by neutralization assay and expressed as GMTs.

Outcome measures

Outcome measures
Measure	RSV MAT Group - Infant n=140 Participants This group consisted of infants born to mothers (from RSV MAT Group - Mother) who received a single dose of RSV MAT vaccine during pregnancy.	Placebo Group - Infant n=67 Participants This group consisted of infants born to mothers (from Placebo Group - Mother) who received a single dose of placebo during pregnancy.
RSV-A Neutralizing Antibody Titers for Infant Participants at Day 43 Post-birth	4042.1 Titers Interval 3530.3 to 4628.2	311.3 Titers Interval 250.3 to 387.2

SECONDARY outcome

Timeframe: At Day 121 post-birth

RSV-A neutralizing titers were determined by neutralization assay and expressed as GMTs.

Outcome measures

Outcome measures
Measure	RSV MAT Group - Infant n=50 Participants This group consisted of infants born to mothers (from RSV MAT Group - Mother) who received a single dose of RSV MAT vaccine during pregnancy.	Placebo Group - Infant n=23 Participants This group consisted of infants born to mothers (from Placebo Group - Mother) who received a single dose of placebo during pregnancy.
RSV-A Neutralizing Antibody Titers for Infant Participants at Day 121 Post-birth	682.4 Titers Interval 520.2 to 895.3	74.8 Titers Interval 46.5 to 120.2

SECONDARY outcome

Timeframe: At Day 181 post-birth

RSV-A neutralizing titers were determined by neutralization assay and expressed as GMTs.

Outcome measures

Outcome measures
Measure	RSV MAT Group - Infant n=44 Participants This group consisted of infants born to mothers (from RSV MAT Group - Mother) who received a single dose of RSV MAT vaccine during pregnancy.	Placebo Group - Infant n=9 Participants This group consisted of infants born to mothers (from Placebo Group - Mother) who received a single dose of placebo during pregnancy.
RSV-A Neutralizing Antibody Titers for Infant Participants at Day 181 Post-birth	506.0 Titers Interval 432.4 to 592.3	133.7 Titers Interval 52.4 to 341.2

SECONDARY outcome

Timeframe: At delivery

Population: The analysis was performed on the Per Protocol - Immunogenicity set for maternal participants, which included all maternal participants who received the study intervention to which they were randomized and had post-vaccination immunogenicity data available for the specified analysis at the specified time point (i.e. delivery) minus those participants with protocol deviations that led to exclusion.

RSV MAT IgG-specific antibody concentrations were determined by enzyme-linked immunosorbent assay (ELISA) and expressed as geometric mean concentrations (GMCs) in ELISA units per milliliter (ELU/mL).

Outcome measures

Outcome measures
Measure	RSV MAT Group - Infant n=405 Participants This group consisted of infants born to mothers (from RSV MAT Group - Mother) who received a single dose of RSV MAT vaccine during pregnancy.	Placebo Group - Infant n=178 Participants This group consisted of infants born to mothers (from Placebo Group - Mother) who received a single dose of placebo during pregnancy.
RSV MAT Immunoglobulin G (IgG)-Specific Antibody Concentrations for Maternal Participants at Delivery	62880 ELU/mL Interval 58517.0 to 67568.0	5600 ELU/mL Interval 4949.0 to 6338.0

SECONDARY outcome

Timeframe: At delivery or within 72 hours after birth (only if no cord blood sample could be obtained at delivery)

Population: The analysis was performed on the Per Protocol - Immunogenicity set for infants, which included all infant participants in the Exposed set who had post-delivery/birth immunogenicity data available for the specified analysis at the specified time points (i.e. at delivery or within 72 hours after birth), minus those who (a) were born less than 4 weeks post-maternal participant vaccination and/ or (b) had protocol deviations that led to exclusion.

RSV MAT IgG-specific antibody concentrations were determined by ELISA and expressed as GMCs in ELU/mL. The antibody concentrations were measured on the cord blood sample collected at delivery, or on a blood sample collected from the infant within 72 hours after birth (only if no cord blood sample could be obtained at delivery).

Outcome measures

Outcome measures
Measure	RSV MAT Group - Infant n=230 Participants This group consisted of infants born to mothers (from RSV MAT Group - Mother) who received a single dose of RSV MAT vaccine during pregnancy.	Placebo Group - Infant n=97 Participants This group consisted of infants born to mothers (from Placebo Group - Mother) who received a single dose of placebo during pregnancy.
RSV MAT IgG-specific Antibody Concentrations for Infant Participants at Delivery or Within 72 Hours After Birth	94365 ELU/mL Interval 86569.0 to 102864.0	6610 ELU/mL Interval 5688.0 to 7682.0

SECONDARY outcome

Timeframe: At delivery (for maternal participants) or within 72 hours after birth (for infant participants, only if no cord blood could be obtained)

Population: The analysis was performed on all pairs of maternal participants (from Per Protocol -Immunogenicity set for maternal participants) and their infants (from Per Protocol - Immunogenicity set for infants) with available results for this outcome measure at the specified time points.

The placental transfer ratio of RSV-MAT IgG-specific antibody concentration was determined from cord blood over that of the blood sample from mother at delivery. If no cord blood could be obtained, an infant blood sample was collected 72 hours after birth.

Outcome measures

Outcome measures
Measure	RSV MAT Group - Infant n=150 Participants This group consisted of infants born to mothers (from RSV MAT Group - Mother) who received a single dose of RSV MAT vaccine during pregnancy.	Placebo Group - Infant n=60 Participants This group consisted of infants born to mothers (from Placebo Group - Mother) who received a single dose of placebo during pregnancy.
Geometric Mean Ratio (GMR) Between Cord Blood and Maternal RSV MAT Immunoglobulin G (IgG)-Specific Antibody Concentrations	1.46 Ratio Interval 1.35 to 1.58	1.39 Ratio Interval 1.22 to 1.59

SECONDARY outcome

Timeframe: From Day 1 to Day 7 included

Population: The analysis was performed on the Solicited Safety set for maternal participants, which included all maternal participants who received the study intervention and who had solicited safety data available during the specified period (i.e. from Day 1 to Day 7 included).

Assessed solicited administration site events included erythema, pain and swelling at the injection site. Any pain = occurrence of the symptom regardless of intensity grade. Any erythema and swelling = symptom reported with a surface diameter greater than or equal to 20 millimeters.

Outcome measures

Outcome measures
Measure	RSV MAT Group - Infant n=3090 Participants This group consisted of infants born to mothers (from RSV MAT Group - Mother) who received a single dose of RSV MAT vaccine during pregnancy.	Placebo Group - Infant n=1547 Participants This group consisted of infants born to mothers (from Placebo Group - Mother) who received a single dose of placebo during pregnancy.
Number of Maternal Participants With Any Solicited Administration Site Events From Day 1 to Day 7 Included Any Erythema	133 Participants	8 Participants
Number of Maternal Participants With Any Solicited Administration Site Events From Day 1 to Day 7 Included Any Pain	1294 Participants	230 Participants
Number of Maternal Participants With Any Solicited Administration Site Events From Day 1 to Day 7 Included Any Swelling	96 Participants	8 Participants

SECONDARY outcome

Timeframe: From Day 1 to Day 7 included

Assessed solicited systemic events included abdominal pain, diarrhea, fatigue, headache, nausea, fever \[temperature equal to or above (\>=) 38 degrees Celsius (°C)/100.4 degrees Fahrenheit (°F), regardless of the location of measurement\] and vomiting. Any = occurrence of the adverse event regardless of intensity grade or relation to study vaccination.

Outcome measures

Outcome measures
Measure	RSV MAT Group - Infant n=3090 Participants This group consisted of infants born to mothers (from RSV MAT Group - Mother) who received a single dose of RSV MAT vaccine during pregnancy.	Placebo Group - Infant n=1547 Participants This group consisted of infants born to mothers (from Placebo Group - Mother) who received a single dose of placebo during pregnancy.
Number of Maternal Participants With Any Solicited Systemic Events From Day 1 to Day 7 Included Any Fatigue	1091 Participants	479 Participants
Number of Maternal Participants With Any Solicited Systemic Events From Day 1 to Day 7 Included Any Headache	942 Participants	442 Participants
Number of Maternal Participants With Any Solicited Systemic Events From Day 1 to Day 7 Included Any Nausea	599 Participants	306 Participants
Number of Maternal Participants With Any Solicited Systemic Events From Day 1 to Day 7 Included Any Abdominal pain	492 Participants	231 Participants
Number of Maternal Participants With Any Solicited Systemic Events From Day 1 to Day 7 Included Any Diarrhea	351 Participants	180 Participants
Number of Maternal Participants With Any Solicited Systemic Events From Day 1 to Day 7 Included Any Fever	26 Participants	7 Participants
Number of Maternal Participants With Any Solicited Systemic Events From Day 1 to Day 7 Included Any Vomiting	276 Participants	149 Participants

SECONDARY outcome

Timeframe: From Day 1 to Day 30 included

Population: The analysis was performed on the Exposed Set for maternal participants, which included all maternal participants who received the study intervention.

An unsolicited AE is defined as any AE reported in addition to those solicited during the clinical study. Also, any 'solicited' symptom with onset outside the specified period of follow-up for solicited symptoms was reported as an unsolicited AE. Any = occurrence of any unsolicited AE regardless of intensity grade or relation to vaccination.

Outcome measures

Outcome measures
Measure	RSV MAT Group - Infant n=3557 Participants This group consisted of infants born to mothers (from RSV MAT Group - Mother) who received a single dose of RSV MAT vaccine during pregnancy.	Placebo Group - Infant n=1771 Participants This group consisted of infants born to mothers (from Placebo Group - Mother) who received a single dose of placebo during pregnancy.
Number of Maternal Participants With Any Unsolicited AEs From Day 1 to Day 30 Included	629 Participants	297 Participants

SECONDARY outcome

Timeframe: From Day 1 to Day 181 post-delivery

Population: The analysis was performed on the Exposed Set for maternal participants, which included all maternal participants who received the study intervention.

An SAE is defined as any untoward medical occurrence that resulted in death, was life-threatening, required hospitalization or prolongation of existing hospitalization, resulted in disability/incapacity, was a congenital anomaly/birth defect in the offspring of a study participant or resulted in abnormal pregnancy outcomes or in other situations that were considered serious per medical or scientific judgment. At least one SAE = occurrence of at least one SAE regardless of intensity grade or relation to vaccination.

Outcome measures

Outcome measures
Measure	RSV MAT Group - Infant n=3557 Participants This group consisted of infants born to mothers (from RSV MAT Group - Mother) who received a single dose of RSV MAT vaccine during pregnancy.	Placebo Group - Infant n=1771 Participants This group consisted of infants born to mothers (from Placebo Group - Mother) who received a single dose of placebo during pregnancy.
Number of Maternal Participants With at Least One SAE From Day 1 to Day 181 Post-delivery	827 Participants	395 Participants

SECONDARY outcome

Timeframe: From Day 1 to Day 181 post-delivery

Population: The analysis was performed on the Exposed Set for maternal participants, which included all maternal participants who received the study intervention.

Outcome measures

Outcome measures
Measure	RSV MAT Group - Infant n=3557 Participants This group consisted of infants born to mothers (from RSV MAT Group - Mother) who received a single dose of RSV MAT vaccine during pregnancy.	Placebo Group - Infant n=1771 Participants This group consisted of infants born to mothers (from Placebo Group - Mother) who received a single dose of placebo during pregnancy.
Number of Maternal Participants With at Least One AE Leading to Study Withdrawal From Day 1 to Day 181 Post-delivery	6 Participants	3 Participants

SECONDARY outcome

Timeframe: From Day 1 to Day 181 post-delivery

Population: The analysis was performed on the Exposed Set for maternal participants, which included all maternal participants who received the study intervention.

All-cause MA-RTI occurred when the maternal participant visited a healthcare professional (e.g., a General Practitioner) for any respiratory symptom, including (but not limited to) cough, sore throat, sputum production and difficulty breathing. At least one all-cause MA-RTI = occurrence of at least one all-cause MA-RTI regardless of intensity grade or relation to vaccination.

Outcome measures

Outcome measures
Measure	RSV MAT Group - Infant n=3557 Participants This group consisted of infants born to mothers (from RSV MAT Group - Mother) who received a single dose of RSV MAT vaccine during pregnancy.	Placebo Group - Infant n=1771 Participants This group consisted of infants born to mothers (from Placebo Group - Mother) who received a single dose of placebo during pregnancy.
Number of Maternal Participants With at Least One All-cause MA-RTI From Day 1 to Day 181 Post-delivery	317 Participants	144 Participants

SECONDARY outcome

Timeframe: From Day 1 to Day 42 post-delivery, an average of 2 months

Population: The analysis was performed on the Exposed Set for maternal participants, which included all maternal participants who received the study intervention.

Outcome measures

Outcome measures
Measure	RSV MAT Group - Infant n=3557 Participants This group consisted of infants born to mothers (from RSV MAT Group - Mother) who received a single dose of RSV MAT vaccine during pregnancy.	Placebo Group - Infant n=1771 Participants This group consisted of infants born to mothers (from Placebo Group - Mother) who received a single dose of placebo during pregnancy.
Number of Maternal Participants With at Least One MAE From Day 1 to Day 42 Post-delivery	1717 Participants	785 Participants

SECONDARY outcome

Timeframe: From Day 1 to Day 42 post-delivery, an average of 2 months

Population: The analysis was performed on the Exposed Set for maternal participants, which included all maternal participants who received the study intervention.

Assessed pregnancy outcomes included live birth with no congenital anomalies, live birth with minor congenital anomaly(ies), live birth with at least 1 major congenital anomaly, fetal death/still birth with no congenital anomalies, fetal death/still birth with at least 1 major congenital anomaly and unknown outcome (includes participants withdrawn before/at delivery with no available data of pregnancy outcomes).

Outcome measures

Outcome measures
Measure	RSV MAT Group - Infant n=3557 Participants This group consisted of infants born to mothers (from RSV MAT Group - Mother) who received a single dose of RSV MAT vaccine during pregnancy.	Placebo Group - Infant n=1771 Participants This group consisted of infants born to mothers (from Placebo Group - Mother) who received a single dose of placebo during pregnancy.
Number of Maternal Participants With Pregnancy Outcomes From Day 1 to Day 42 Post-delivery Live birth with no congenital anomalies	3118 Participants	1555 Participants
Number of Maternal Participants With Pregnancy Outcomes From Day 1 to Day 42 Post-delivery Live birth with only minor congenital anomaly(ies)	317 Participants	143 Participants
Number of Maternal Participants With Pregnancy Outcomes From Day 1 to Day 42 Post-delivery Live birth with at least 1 major congenital anomaly	61 Participants	43 Participants
Number of Maternal Participants With Pregnancy Outcomes From Day 1 to Day 42 Post-delivery Fetal death/still birth with no congenital anomalies	9 Participants	6 Participants
Number of Maternal Participants With Pregnancy Outcomes From Day 1 to Day 42 Post-delivery Fetal death/still birth with at least 1 major congenital anomaly	2 Participants	0 Participants
Number of Maternal Participants With Pregnancy Outcomes From Day 1 to Day 42 Post-delivery Unknown outcome	50 Participants	24 Participants

SECONDARY outcome

Timeframe: From Day 1 to Day 42 post-delivery, an average of 2 months

Population: The analysis was performed on the Exposed Set for maternal participants, which included all maternal participants who received the study intervention.

Pregnancy-related AESIs included chorioamnionitis, fetal growth restriction, gestational diabetes mellitus, gestational hypertension, pre-eclampsia, pre-eclampsia with severe features including eclampsia, maternal death, premature preterm rupture of membranes, preterm labor, provider-initiated preterm birth.

Outcome measures

Outcome measures
Measure	RSV MAT Group - Infant n=3557 Participants This group consisted of infants born to mothers (from RSV MAT Group - Mother) who received a single dose of RSV MAT vaccine during pregnancy.	Placebo Group - Infant n=1771 Participants This group consisted of infants born to mothers (from Placebo Group - Mother) who received a single dose of placebo during pregnancy.
Number of Maternal Participants With Pregnancy-related Adverse Events of Special Interest (AESIs) From Day 1 to Day 42 Post-delivery Preterm Labor	141 Participants	57 Participants
Number of Maternal Participants With Pregnancy-related Adverse Events of Special Interest (AESIs) From Day 1 to Day 42 Post-delivery Chorioamnionitis	30 Participants	14 Participants
Number of Maternal Participants With Pregnancy-related Adverse Events of Special Interest (AESIs) From Day 1 to Day 42 Post-delivery Fetal Growth Restriction	30 Participants	26 Participants
Number of Maternal Participants With Pregnancy-related Adverse Events of Special Interest (AESIs) From Day 1 to Day 42 Post-delivery Gestational Diabetes Mellitus	42 Participants	19 Participants
Number of Maternal Participants With Pregnancy-related Adverse Events of Special Interest (AESIs) From Day 1 to Day 42 Post-delivery Gestational Hypertension	85 Participants	41 Participants
Number of Maternal Participants With Pregnancy-related Adverse Events of Special Interest (AESIs) From Day 1 to Day 42 Post-delivery Pre-Eclampsia	74 Participants	36 Participants
Number of Maternal Participants With Pregnancy-related Adverse Events of Special Interest (AESIs) From Day 1 to Day 42 Post-delivery Pre-Eclampsia With Severe Features Including Eclampsia	58 Participants	28 Participants
Number of Maternal Participants With Pregnancy-related Adverse Events of Special Interest (AESIs) From Day 1 to Day 42 Post-delivery Maternal Death	2 Participants	1 Participants
Number of Maternal Participants With Pregnancy-related Adverse Events of Special Interest (AESIs) From Day 1 to Day 42 Post-delivery Premature Preterm Rupture Of Membranes	53 Participants	20 Participants
Number of Maternal Participants With Pregnancy-related Adverse Events of Special Interest (AESIs) From Day 1 to Day 42 Post-delivery Provider-Initiated Preterm Birth	54 Participants	16 Participants

SECONDARY outcome

Timeframe: From birth to Day 42 post-birth, an average of 2 months

Population: The analysis was performed on the Exposed Set for infants, which included infants live-born to exposed maternal participants, whose parents/LARs completed the informed consent process and signed the informed consent form.

Neonatal/infant AESIs included congenital anomalies with functional defects, congenital anomalies with internal structural defects, congenital anomalies with major external structural defects, extremely low birth weight (\<1000 grams), low birth weight (\<2500 grams), very low birth weight (\<1500 grams), neonatal death in a preterm live birth (gestational age \>=28 and \<37 weeks), neonatal death in a term live birth (\>=37 weeks of gestational age), neonatal death in an extremely pre-term birth (gestational age \>=22 and \<28 weeks), preterm birth (\<37 weeks of gestational age), small for gestational age.

Outcome measures

Outcome measures
Measure	RSV MAT Group - Infant n=3494 Participants This group consisted of infants born to mothers (from RSV MAT Group - Mother) who received a single dose of RSV MAT vaccine during pregnancy.	Placebo Group - Infant n=1741 Participants This group consisted of infants born to mothers (from Placebo Group - Mother) who received a single dose of placebo during pregnancy.
Number of Infant Participants With Neonatal AESIs From Birth to Day 42 Post-birth Congenital Anomalies With Functional Defects	5 Participants	2 Participants
Number of Infant Participants With Neonatal AESIs From Birth to Day 42 Post-birth Congenital Anomalies With Internal Structural Defects	23 Participants	16 Participants
Number of Infant Participants With Neonatal AESIs From Birth to Day 42 Post-birth Congenital Anomalies With Major External Structural Defects	24 Participants	14 Participants
Number of Infant Participants With Neonatal AESIs From Birth to Day 42 Post-birth Extremely Low Birth Weight (<1000 grams)	3 Participants	0 Participants
Number of Infant Participants With Neonatal AESIs From Birth to Day 42 Post-birth Low Birth Weight (<2500 grams)	196 Participants	102 Participants
Number of Infant Participants With Neonatal AESIs From Birth to Day 42 Post-birth Very Low Birth Weight (<1500 grams)	5 Participants	0 Participants
Number of Infant Participants With Neonatal AESIs From Birth to Day 42 Post-birth Neonatal Death In A Preterm Live Birth (Gestational Age >=28 and <37 Weeks)	5 Participants	0 Participants
Number of Infant Participants With Neonatal AESIs From Birth to Day 42 Post-birth Neonatal Death In A Term Live Birth (>= 37 Weeks Of Gestational Age)	6 Participants	3 Participants
Number of Infant Participants With Neonatal AESIs From Birth to Day 42 Post-birth Neonatal Death In An Extremely Pre-Term Birth (Gestational Age >=22 and <28 Weeks)	2 Participants	0 Participants
Number of Infant Participants With Neonatal AESIs From Birth to Day 42 Post-birth Preterm Birth (<37 Weeks Of Gestational Age)	237 Participants	86 Participants
Number of Infant Participants With Neonatal AESIs From Birth to Day 42 Post-birth Small For Gestational Age	253 Participants	161 Participants

Adverse Events

RSV MAT Group - Mother

Serious events: 827 serious events

Other events: 2561 other events

Deaths: 2 deaths

Placebo Group - Mother

Serious events: 395 serious events

Other events: 1175 other events

Deaths: 1 deaths

RSV MAT Group - Infant

Serious events: 731 serious events

Other events: 2615 other events

Deaths: 20 deaths

Placebo Group - Infant

Serious events: 371 serious events

Other events: 1293 other events

Deaths: 4 deaths

Serious adverse events

Other adverse events

Additional Information

GSK Response Center

GlaxoSmithKline

Phone: 866-435-7343

Email: [email protected]

Results disclosure agreements

Principal investigator is a sponsor employee GSK agreements may vary with individual investigators, but will not prohibit any investigator from publishing. GSK supports the publication of results from all centers of a multi-center trial but requests that reports based on single site data not precede the primary publication of the entire clinical trial.
Publication restrictions are in place

Restriction type: OTHER