Trial Outcomes & Findings for COVID-19 Antibody and Reinfection Study (NCT NCT05365750)

NCT ID: NCT05365750

Last Updated: 2025-09-18

Results Overview

In this case-control analysis, case patients were participants with the outcome of reinfection. The date of reinfection was the index date. Control patients were those with a primary infection but without the outcome reinfection by the index date. The case and control participants were compared with respect to a seronegative test result (exposure) after primary infection and closest in time to the index date. Because the cases and controls were selected on the basis of the outcome, the seronegative result is listed below by case and control status.

• Recruitment status: COMPLETED
• Target enrollment: 4235 participants
• Primary outcome timeframe: Through the completion of the study analytic period, an average of 6 months
• Results posted on: 2025-09-18

Participant Flow

Participants were recruited into a cohort from the health plan membership from June 2020 to March 2021 using text message and emails linked to online consent documents. From this cohort, we conducted a nested case control analysis in which participants with the outcome were compared to participants without the outcome.

As is standard in a nested case-control study, the cohort is used to identify a sufficient sample to conduct the case-control analysis, in which people with the outcome of interest are compared with people who did not have the outcome. The protocol section describes the recruited cohort (n=4235) and the results section describe participants in the case-control (n=1114). Participants not in the case-control (n=3121) are not in the participant flow because their data were not analyzed.

Participant milestones

Measure	Case Patients Nested Within the Cohort Case patients had a reinfection, defined as a positive SARS-CoV-2 RNA test ≥ 90 days after the first positive RNA. Case patients had serology completed between the infections.	Control Patients Nested Within the Cohort Control patients had a primary infection and serologic tests that were conducted between the primary infection and the index date. A control patient could be matched to more than one case patient if they had more than one eligible serologic test. Case patients were 1:20 matched to controls.
Overall Study STARTED	80	1034
Overall Study COMPLETED	80	1034
Overall Study NOT COMPLETED	0	0

Reasons for withdrawal

Withdrawal data not reported

Baseline Characteristics

COVID-19 Antibody and Reinfection Study

Baseline characteristics by cohort

Measure	Case Patients Nested Within the Cohort n=80 Participants Case patients had a reinfection, defined as a positive SARS-CoV-2 RNA test ≥ 90 days after the first positive RNA. Case patients had serology completed between the infections.	Control Patients Nested Within the Cohort n=1034 Participants Control patients had a primary infection and serologic tests that were conducted between the primary infection and the index date. A control patient could be matched to more than one case patient if they had more than one eligible serologic test. Case patients were 1:20 matched to controls.	Total n=1114 Participants Total of all reporting groups
Age, Continuous	52.7 years STANDARD_DEVIATION 12.7 • n=5 Participants	54.4 years STANDARD_DEVIATION 11.9 • n=7 Participants	54.3 years STANDARD_DEVIATION 11.9 • n=5 Participants
Sex: Female, Male Female	60 Participants n=5 Participants	761 Participants n=7 Participants	821 Participants n=5 Participants
Sex: Female, Male Male	20 Participants n=5 Participants	273 Participants n=7 Participants	293 Participants n=5 Participants
Ethnicity (NIH/OMB) Hispanic or Latino	32 Participants n=5 Participants	252 Participants n=7 Participants	284 Participants n=5 Participants
Ethnicity (NIH/OMB) Not Hispanic or Latino	48 Participants n=5 Participants	782 Participants n=7 Participants	830 Participants n=5 Participants
Ethnicity (NIH/OMB) Unknown or Not Reported	0 Participants n=5 Participants	0 Participants n=7 Participants	0 Participants n=5 Participants
Negative serologic test	12 participants n=5 Participants	77 participants n=7 Participants	89 participants n=5 Participants

PRIMARY outcome

Timeframe: Through the completion of the study analytic period, an average of 6 months

Population: Study cohort members with a primary SARS-CoV-2 infection

In this case-control analysis, case patients were participants with the outcome of reinfection. The date of reinfection was the index date. Control patients were those with a primary infection but without the outcome reinfection by the index date. The case and control participants were compared with respect to a seronegative test result (exposure) after primary infection and closest in time to the index date. Because the cases and controls were selected on the basis of the outcome, the seronegative result is listed below by case and control status.

Outcome measures

Measure	Case Patients n=80 Participants Participants with reinfection, defined as a positive SARS-CoV-2 RNA test ≥ 90 days after the first positive RNA test	Control Patients n=1034 Participants Participants without reinfection
Reinfection With SARS-CoV-2 Seronegative test results	12 Participants	77 Participants
Reinfection With SARS-CoV-2 Seropositive test results	68 Participants	957 Participants

Adverse Events

Case Patients Nested Within the Cohort

Serious events: 0 serious events

Other events: 0 other events

Deaths: 0 deaths

Control Patients Nested Within the Cohort

Serious events: 0 serious events

Other events: 0 other events

Deaths: 0 deaths

Serious adverse events

Adverse event data not reported

Other adverse events

Adverse event data not reported

Additional Information

Ingrid A Binswanger, MD, MPH

Kaiser Permanente Colorado

Phone: 720-416-7104

Email: ingrid.a.binswanger@kp.org

Results disclosure agreements

• Principal investigator is a sponsor employee
• Publication restrictions are in place