Phase 1 is the open-label dose-finding portion of the study to evaluate the safety, tolerability, and immunogenicity of BNT162b2 on a 2-dose (separated by approximately 21 days) schedule in 3 age groups (participants ≥5 to <12 years, ≥2 to <5 years, and ≥6 months to <2 years of age). Dose finding is being initiated in this study in participants ≥5 to <12 years of age based on the acceptable blinded safety assessment of the 30-μg dose in 12- to 15-year-olds in the C4591001 study.

The purpose of Phase 1 is to identify preferred dose level(s) of BNT162b2 from up to 3 different dose levels in each age group.

Phase 2/3 will evaluate the safety, tolerability, and immunogenicity in each age group at the selected dose level from Phase 1. Efficacy will be evaluated across all age groups in which immunobridging is successful, depending on the accrual of a sufficient number of cases across those age groups.

All participants will have blood drawn at baseline prior to Dose 1 and 6 months after Dose 2. Immunobridging to participants 16 to 25 years of age in the C4591001 study will be based on immunogenicity data collected at baseline and 1 month after Dose 2. The persistence of the immune response will be based on immunogenicity data collected in participants at baseline and at 1, 6, 12 (original BNT162b2 group only), and 24 months after Dose 2 (original BNT162b2 group only). In addition, efficacy against confirmed COVID-19 and against asymptomatic infection will also be assessed.

At the 6-month follow-up visit, all participants will be unblinded. Participants who originally received a placebo will be offered the opportunity to receive BNT162b2 as part of the study.

Approximately 450 participants (300 in the active vaccine group and 150 in the placebo group) randomized in each age group in this phase will contribute to the immunobridging analysis at 1 month after Dose 2 and will contribute to the overall analysis of the persistence of immune response at 6 months after Dose 2. These participants will be enrolled from both US and EU sites to ensure this subset is representative of the whole study.

For the persistence time points of 12 and 24 months after Dose 2, approximately 70 participants from each age group in the original BNT162b2 vaccine group will have an immunogenicity blood draw in order to contribute to the analysis. All approximately 4500 participants will contribute to the VE analysis for conditional VE and asymptomatic infection. Efficacy will be evaluated across all age groups in which immunobridging is successful, depending on the accrual of a sufficient number of cases across those age groups.

Results

Pfizer and BioNTech announced results from this trial.

The Companies announced favorable safety profile and robust neutralizing antibody responses in children 5 to 11 years of age using a two-dose regimen of 10 µg administered 21 days apart, a smaller dose than the 30 µg dose used for people 12 and older.

The antibody responses in the participants given 10 µg doses were comparable to those recorded in a previous Pfizer-BioNTech study in people 16 to 25 years of age immunized with 30 µg doses.

The 10 µg dose was carefully selected as the preferred dose for safety, tolerability and immunogenicity in children 5 to 11 years of age. These are the first results from a pivotal trial of a COVID-19 vaccine in this age group.