The Phase 1/2 evaluation supported advancing BNT162b2 at 30 µg into Phase 2/3 evaluation in adults aged 18–85. BNT162b1 and BNT162b2 elicited comparable immune responses, but BNT162b2 had milder systemic reactogenicity, particularly among adults aged 65–85. Immunogenicity declined with age but remained above the convalescent-serum panel baseline. Limitations included the absence of safety and immunogenicity data beyond seven days after dose 2 and uncertainty about how measured humoral and cellular responses related to protection from COVID-19. Larger studies with more diverse participants were planned to address these limitations.