In this ongoing multinational trial, placebo-controlled and observer-blinded, funded by BioNTech and Pfizer, 2,260 adolescents aged 12-15 years were randomly assigned 1:1 to receive two injections, 21 days apart, of 30 μg of BNT162b2 (1131 participants) or placebo (1129 participants). The sought results were non-inferiority of the immune response, safety (reactogenicity and adverse events), and efficacy (against Covid-19 after 7 days of dose 2) in the 12-15 year-old cohort. BNT162b2 was found to have a favorable safety profile; mild to moderate reactogenicity (predominantly injection site pain [79-86%], fatigue [60-66%], and headache [55-65%]); no vaccine-related serious adverse events and few serious adverse events overall. The ratio of the geometric mean of the 50% neutralizing titers of SARS-CoV-2 after dose 2 in participants aged 12 to 15 years relative to participants aged 16 to 25 years was 1.76 (CI = 95%, 1.47 to 2.10), meeting the non-inferiority criterion (greater than 0.67) indicating a greater response. The observed vaccine efficacy was 100% (95% CI, 75.3 to 100). It was concluded that the BNT162b2 vaccine in recipients aged 12 to 15 years had a favorable safety profile, produced a greater immune response than in young adults, and was highly effective against Covid-19.