Table 1. Description of identified clinical studies, type, purpose and result/conclusion.

VRBPAC- Vaccine Related and Biological Product Advisory Committee

Author	Date of Publication	Study Type	Study Purpose	Result/Conclusion
Pfizer FDA VRBPAC  [17]	12/10/2020	Subgroup Analysis of a Randomized Controlled Study	Pivotal trial to estimate Pfizer vaccine safety and efficacy overall, and within various subgroups. Subgroup analysis of previously infected provided.	Overall, 3% of all participants had prior infection with SARS-CoV-2. There were 1/567 (0.2%) and 1/526 (0.2%) reinfections in placebo and vaccination arms respectively.  The overall incidence of unvaccinated and vaccinated incidence was 0.93% and 0.05%, respectively.
Moderna FDA VRBPAC [18]	12/17/2020	Subgroup Analysis of a Randomized Control Study	Pivotal trial to estimate Moderna vaccine safety and efficacy overall, and within various subgroups. Subgroup analysis of previously infected provided.	Overall, 0.15% of participants had baseline SARS-CoV2 seropositivity. There was 1/334 (0.3%)  and 0/341 (0.0%) reinfections in the placebo and vaccination arms respectively. The overall incidence of infection in vaccinated seronegative participants was (<0.1%)
J&J FDA VRBPAC [19]	2/26/2021	Subgroup Analysis of a Randomized Control Study	Pivotal trial to estimate Johnson and Johnson vaccine safety and efficacy overall, and within various subgroups. Subgroup analysis of previously infected provided.	Overall, 9.6% of all participants had baseline SARS-CoV-2 seropositivity. There were 4/2030 (0.2%) and 3/2122 (0.14%) reinfection in the placebo and vaccination arms respectively.  The incidence of primary infection in vaccinated seronegative participants was 0.8%.
Goldberg et. al. [20]	4/24/2021	Prospective Observational Analysis	To estimate vaccine efficacy vs. natural immunity, to varying severities of disease, stratified amongst age groups.	Study found excellent overall vaccine efficacy against infection, hospitalization and death (92.8%, 94.2%, 94.4%, 93.7%) . Previously infected individuals also had excellent protection to infection, hospitalization and illness (94.8%, 94.1%, 96.4%).  Superior efficacy held up in every age group, for each severity.
Shrestha et. al. [21]	6/5/2021	Retrospective Observational Cohort	To assess for reinfection in previously infected (with/without vaccination), vaccinated (Pz, Md)  and unvaccinated HCWs between 12/16/20-5/15/2021.	No reinfections (0.0%) in any HCW with previous infection, regardless of vaccination status. Vaccination in COVID naïve HCWS was (0.7%). No statistically significant benefit in vaccinating previously infected individuals (HR 0.313 [95% CI 0 to Inf])
Lumley et al. [22]	7/3/2021	Retrospective Observational Cohort	To study the incidence  SARS-COV-2 infection (Alpha strain)  in HCWS, according to antibody and vaccination (PZ, AZ) status.	When compared to unvaccinated seronegative individuals, aRR for vaccinated immunity and previous infection were 90% [62-98%]  and 85% [74-92%], respectively .
Cavanaugh et. al. [23]	8/13/2021	Case-control study	To determine the relative odds of non-vaccination (PZ, Md, JnJ) in newly reinfected and matched uninfected/recovered controls, in May/June 2021 in Kentucky.	Reinfection in previously infected individuals was associated with a 2.34x [1.58-3.57] odds of non-vaccinated status.
Satwik et. al. [24]	8/15/2021	Retrospective Observational Cohort	To assess vaccination efficacy (AZ) and previous infection in preventing symptomatic, severe disease, and death in one tertiary hospital in India, where the Delta variant is suspected to be the dominant strain.	Previous infection was significantly protective against symptomatic and  moderate/severe disease with 93% [87-96%] and 89% [57-97%] effectiveness, respectively.  Two doses of AZ vaccine led to reduction of symptomatic and moderate/severe disease by 24% [6-38%] and 65% [42-79%].
Gazit et. al. [25]	8/24/2021	Retrospective Observational Analysis	To compare reinfection in previously infected individuals with and without vaccination, to a naïve vaccinated control.	Found prior infection afforded 13x protection from reinfection, compared to never infected but vaccinated individuals – when prior infection and vaccination were matched for time. Prior infection afforded 5.97x protection when unmatched for time.  Vaccination resulted in 0.53x odds of reinfection, in previously infected group.