A Trial Investigating the Safety and Effects of Four BNT162 Vaccines Against COVID-19 in Healthy and Immunocompromised Adults

This study was a multi-site, Phase I/II, open-label, dose-escalation study. The study included the first-in-human (FIH) dose and dose ranging groups for all four vaccines in healthy younger participants (aged 18 to 55 years \[years\]) and older participants (aged 56 to 85 years). The conducted Part A followed a dose escalation design. Discretionary dose de-escalation and refinement was also planned. Study participants with the FIH immunization and any subsequent dose escalation cohorts were immunized using a sentinel dosing/subject staggering. For any dose de-escalation or dose-refinement cohorts in younger adults, i.e., cohorts with doses lower than previously tested, participants were dosed using a subject staggering process. Cohorts in older participants were optional and dependent on acceptability of dosing in younger participants. Part A consisted of a treatment phase and a follow-up phase. For the BNT162a1 3 µg arm, the Safety Review Committee (SRC) decided to stop dosing after 6 treated participants and to not administer the boost immunization (Dose 2). For the BNT162b1 60 µg arm, the SRC decided to not administer the boost immunization (Dose 2) for the 12 participants.