14.1 Immunogenicity Data Supporting the Use of a Single Dose of COMIRNATY in Seropositive, Vaccine-Naïve Individuals

In a post-hoc analysis in a subset of participants 18 through 85 years of age enrolled in Study 7 (NCT05004181), immunogenicity of a single 30 mcg dose of a Pfizer-BioNTech bivalent COVID-19 vaccine containing equal quantities of modRNA encoding the viral spike (S) glycoprotein for the Alpha and Delta SARS-CoV-2 variants [not authorized or approved in the U.S., hereafter referred to as bivalent vaccine (Alpha and Delta)] was assessed in COVID-19 vaccine-naïve participants with evidence of prior SARS-CoV-2 infection (n = 262) compared to participants without prior SARS-CoV-2 infection who received 2 doses of COMIRNATY in Study 2 (n = 275). Among Study 7 participants, 253 were from study sites in South Africa and 9 were from study sites in the U.S. The immunogenicity of the bivalent Alpha and Delta vaccine is relevant to COMIRNATY because these vaccines are manufactured using the same process with differences only in the encoded spike proteins.

Table 10 presents demographic characteristics for participants in the immunogenicity analysis set.

The objective of this analysis was to assess noninferiority with respect to level of 50% neutralizing titer (NT50) and to the seroresponse rate to the reference strain induced by a single dose of the bivalent Alpha and Delta vaccine in COVID-19 vaccine-naïve participants with evidence of prior infection relative to participants without evidence of SARS-CoV-2 infection who received 2 doses of COMIRNATY.

Noninferiority of the reference strain immune response with respect to level of NT50 was met, as the lower bound of the 2-sided 95% CI for the geometric mean ratio (GMR) was >0.67 (Table 11). Noninferiority of the seroresponse rate to the reference strain was not met, as the lower bound of the 2-sided 95% CIs for the difference in seroresponse rate of reference strain was -10.04%, below the noninferiority margin of -10% (Table 12).

14.2 Primary Series With COMIRNATY – Efficacy in Participants 16 Years of Age and Older

Study 2 is an ongoing, multicenter, multinational, randomized, placebo-controlled, observer-blind, dose-finding, vaccine candidate–selection, and efficacy study in participants 12 years of age and older. Randomization was stratified by age: 12 through 15 years of age, 16 through 55 years of age, or 56 years of age and older, with a minimum of 40% of participants in the ≥56-year stratum. The study excluded participants who were immunocompromised and those who had previous clinical or microbiological diagnosis of COVID-19. Participants with preexisting stable disease, defined as disease not requiring significant change in therapy or hospitalization for worsening disease during the 6 weeks before enrollment, were included as were participants with known stable infection with HIV, hepatitis C virus (HCV), or hepatitis B virus (HBV).

In Study 2, based on data accrued through March 13, 2021, approximately 44,000 participants 12 years of age and older were randomized equally and received 2 doses of COMIRNATY or placebo. Participants are planned to be followed for up to 24 months, for assessments of safety and efficacy against COVID-19.

Overall, among the total participants who received COMIRNATY or placebo, 51.4% or 50.3% were male and 48.6% or 49.7% were female, 79.1% or 79.2% were 16 through 64 years of age, 20.9% or 20.8% were 65 years of age and older, 81.9% or 82.1% were White, 9.5% or 9.6% were Black or African American, 1.0% or 0.9% were American Indian or Alaska Native, 4.4% or 4.3% were Asian, 0.3% or 0.2% Native Hawaiian or other Pacific Islander, 25.6% or 25.4% were Hispanic/Latino, 73.9% or 74.1% were non-Hispanic/Latino, 0.5% or 0.5% did not report ethnicity, 46.0% or 45.7% had comorbidities [participants who have 1 or more comorbidities that increase the risk of severe COVID-19 disease: defined as subjects who had at least 1 of the Charlson comorbidity index category or body mass index (BMI) ≥30 kg/m2], respectively. The mean age at vaccination was 49.8 or 49.7 years and median age was 51.0 or 51.0 in participants who received COMIRNATY or placebo, respectively.

Efficacy Against COVID-19

The population for the analysis of the protocol pre-specified primary efficacy endpoint included 36,621 participants 12 years of age and older (18,242 in the COMIRNATY group and 18,379 in the placebo group) who did not have evidence of prior infection with SARS-CoV-2 through 7 days after the second dose. The population in the protocol pre-specified primary efficacy analysis included all participants 12 years of age and older who had been enrolled from July 27, 2020, and followed for the development of COVID-19 through November 14, 2020. Participants 18 through 55 years of age and 56 years of age and older began enrollment from July 27, 2020, 16 through 17 years of age began enrollment from September 16, 2020, and 12 through 15 years of age began enrollment from October 15, 2020.

For participants without evidence of SARS-CoV-2 infection prior to 7 days after Dose 2, vaccine efficacy against confirmed COVID-19 occurring at least 7 days after Dose 2 was 95.0% (95% credible interval: 90.3, 97.6), which met the pre-specified success criterion. The case split was 8 COVID-19 cases in the COMIRNATY group compared to 162 COVID-19 cases in the placebo group.

The population for the updated vaccine efficacy analysis included participants 16 years of age and older who had been enrolled from July 27, 2020, and followed for the development of COVID-19 during blinded placebo-controlled follow-up through March 13, 2021, representing up to 6 months of follow-up after Dose 2. There were 12,796 (60.8%) participants in the COMIRNATY group and 12,449 (58.7%) in the placebo group followed for ≥4 months after Dose 2 in the blinded placebo-controlled follow-up period.

SARS-CoV-2 variants of concern identified from COVID-19 cases for this age group from this data cutoff include B.1.1.7 (Alpha) and B.1.351 (Beta). Representation of identified variants among cases in vaccine versus placebo recipients did not suggest decreased vaccine effectiveness against these variants.

The updated vaccine efficacy information is presented in Table 13.

Subgroup analyses of vaccine efficacy (although limited by small numbers of cases in some subgroups) did not suggest meaningful differences in efficacy across genders, ethnic groups, geographies, or for participants with obesity or medical comorbidities associated with high risk of severe COVID-19.

Efficacy Against Severe COVID-19

Efficacy analyses of secondary efficacy endpoints supported the benefit of COMIRNATY in preventing severe COVID-19. Vaccine efficacy against severe COVID-19 is presented only for participants with or without prior SARS-CoV-2 infection (Table 14) as the COVID-19 case counts in participants without prior SARS-CoV-2 infection were the same as those in participants with or without prior SARS-CoV-2 infection in both the COMIRNATY and placebo groups.

14.3 Primary Series With COMIRNATY – Efficacy and Immunogenicity in Adolescents 12 Through 15 Years of Age

A descriptive efficacy analysis of Study 2 has been performed in 2,260 adolescents 12 through 15 years of age evaluating confirmed COVID-19 cases accrued up to a data cutoff date of September 2, 2021.

The vaccine efficacy information in adolescents 12 through 15 years of age is presented in Table 15.

In Study 2, an analysis of SARS-CoV-2 50% neutralizing titers (NT50) 1 month after Dose 2 in a randomly selected subset of participants demonstrated non-inferior immune responses (within 1.5-fold) comparing adolescents 12 through 15 years of age to participants 16 through 25 years of age who had no serological or virological evidence of past SARS-CoV-2 infection up to 1 month after Dose 2 (Table 16).

14.4 Booster Dose With COMIRNATY – Immunogenicity of a First Booster Dose in Individuals 18 Through 55 Years of Age

Effectiveness of a booster dose of COMIRNATY was based on an assessment of 50% neutralizing antibody titers (NT50) against SARS-CoV-2 reference strain (USA_WA1/2020) in Study 2 participants 18 through 55 years of age (n = 200 – 212) who had no serological or virological evidence of past SARS‑CoV‑2 infection up to 1 month after the booster vaccination. Analyses of NT50 1 month after the booster dose compared to 1 month after the primary series demonstrated noninferiority for both geometric mean ratio (GMR) [3.26 (97.5% CI: 2.76, 3.86)] and difference in seroresponse rates (percentage) [4.5% (97.5% CI: 1.0, 7.9)]. Seroresponse for a participant was defined as achieving a ≥4-fold rise in NT50 from baseline (before primary series).

14.5 Booster Dose With Pfizer-BioNTech COVID-19 Vaccine, Bivalent – Immunogenicity of a Second Booster Dose in Individuals 12 Years of Age and Older

In an analysis of a subset from Study 5, 105 participants 12 through 17 years of age, 297 participants 18 through 55 years of age, and 286 participants 56 years of age and older who had previously received a 2-dose primary series and 1 booster dose with COMIRNATY received a second booster dose of Pfizer-BioNTech COVID-19 Vaccine, Bivalent. In participants 12 through 17 years of age, 18 through 55 years of age, and 56 years of age and older, 75.2%, 71.7% and 61.5% were positive for SARS-CoV-2 at baseline, respectively.

Analyses of NT50 against Omicron BA.4/BA.5 and against reference strain among participants 56 years of age and older who received a second booster dose of Pfizer-BioNTech COVID-19 Vaccine, Bivalent in Study 5 compared to a subset of participants from Study 4 who received a second booster dose of COMIRNATY demonstrated superiority of Pfizer-BioNTech COVID-19 Vaccine, Bivalent to COMIRNATY based on GMR and noninferiority based on difference in seroresponse rates with respect to anti-Omicron BA.4/BA.5 response, and noninferiority of anti-reference strain immune response based on GMR (Table 17 and Table 18).

Analyses of NT50 against Omicron BA.4/BA.5 among participants 18 through 55 years of age compared to participants 56 years of age and older who received a second booster dose of Pfizer-BioNTech COVID-19 Vaccine, Bivalent in Study 5 demonstrated noninferiority of anti-Omicron BA.4/BA.5 response among participants 18 through 55 years of age to participants 56 years of age and older for both GMR and difference in seroresponse rates (Table 17 and Table 18).

The study also assessed the level of NT50 against the anti-Omicron BA.4/BA.5 and original SARS-CoV-2 strains pre-vaccination and 1 month after vaccination in participants who received a second booster dose (Table 19).

14.6 Concomitant Administration of COMIRNATY With Influenza Vaccine in Individuals 18 Through 64 Years of Age

In Study 8 (NCT05310084), a Phase 3 multicenter, randomized, observer-blind study, 1,134 participants 18 through 64 years of age who had received 3 doses of COMIRNATY at least 3 months prior were randomized in a 1:1 ratio to receive either COMIRNATY concomitantly administered with Influenza Vaccine (Afluria Quadrivalent) followed 1 month later by placebo (Group 1, n = 568) or influenza vaccine with placebo followed 1 month later with COMIRNATY (Group 2, n = 566).

Full-length spike (S)-binding IgG responses to COMIRNATY and influenza strain-specific hemagglutination inhibition (HAI) titers were assessed 1-month post-vaccination in each group.

The non-inferiority criteria (lower bound of the 2-sided 95% CI > 0.67) for the comparison of concomitant administration versus separate administration were met. The GMC ratio of full-length S-binding IgG levels of SARS-CoV-2 Wuhan-Hu 1 strain (Original) (Group 1/Group 2) was 0.83 [95% CI: 0.77, 0.89]. The GMT ratio (Group 1/Group 2) for the 4 strain-specific influenza HAI titers were H1N1 A/Victoria: 0.95 [95% CI: 0.83, 1.09]; H3N2 A/Darwin: 0.96 [95% CI: 0.85, 1.09]; B/Austria: 0.89 [95% CI: 0.77, 1.04]; B/Phuket: 1.00 [95% CI: 0.89, 1.13].

SARS-CoV-2 Wuhan-Hu-1 strain (Original) neutralizing GMTs were descriptively assessed in a subset of participants, 100 participants from Group 1 and 100 participants from Group 2.

The SARS-CoV-2 neutralization assay (NT50 titer) GMTs increased from baseline to 1 month after vaccination with COMIRNATY from 2755.9 to 6773.9 in Group 1 and from 2421.2 to 7886.6 in Group 2.