Subsequently, participants in the placebo group were administered the currently available covid-19 vaccines, including BIV1-CovIran, BBIBP-CorV, ChAdOx1 nCoV-19, PastoCoAd, and SpikoGen. We initially aimed to present the interim analysis based on the 180 day follow-up, as stated in the study protocol. After the request of the ethical committee, we provided the interim report for the Iranian Food and Drug Administration based on a shorter follow-up period (median 83 days) after the second dose, the results of which are presented in this study. The median follow-up duration of other covid-19 vaccine phase 3 trials after the second dose was 99 days for BBV152, 21 112 days for BBIBP-CorV, 47 61 days for ChAdOx1 nCoV-19, 48 two months for ChAdOx1 nCoV-19, 26 and six months for BNT162b2. 49 Moreover, this follow-up was 90 days after the first dose for CoronaVac. 50 The study did not have enough power to assess efficacy by subgroup definitively.