Regulatory Decision Summary for Comirnaty

Data from Study C4591031 and C451001 were provided to support the use of a single booster dose of Comirnaty in individuals 16 and 17 years of age, at least six months following the primary 2-dose series. 

Study C4591031 is an ongoing, randomized, placebo-controlled, observer-blind Phase 3 study to evaluate the safety and efficacy of a booster dose of Comirnaty in participants 16 years of age and older. Approximately 10,000 participants 16 years of age and older who completed a 2-dose primary series of Comirnaty were randomized at a ratio of 1:1 to receive either the booster dose of the vaccine or the placebo, at least 6 months after the primary series.

Among evaluable efficacy participants (16 years of age and older) without evidence of infection with SARS-CoV-2 in the 7 days after receipt of the booster dose (4,695 in the booster  dose group and 4,671 in the placebo group), the vaccine efficacy was 95.3% (2-sided 95% CI: 89.5%, 98.3%), based on 6 cases in the vaccine group and 123 cases in the placebo group. In this analysis, among participants 16 to 17 years of age, 41 participants in the vaccine group and 37 participants in the placebo group, two cases occurred among subjects
16-17 years of age, both of which occurred in placebo recipients.

Non-inferiority of immune responses 1 month after the booster dose of the vaccine compared to 1 month after completion of the primary 2-dose series were demonstrated in 306 participants 18 through 55 years of age in the previously submitted Study C4591001. These data are relevant to individuals 16-17 years of age and support the use of a booster dose in that age group.

Of the evaluable safety participants (16 years of age and older) who received a booster dose of Comirnaty (5,055 participants) or placebo (5,020 participants) in Study C4591031, the median follow-up time was 2.5 months after the booster dose to the data cut-off date (5 October 2021). The study included 90 participants 16 to 17 years of age (46 participants in the vaccine group and 44 participants in the placebo group) for safety analysis.

Any adverse events (AEs) were reported by 23.4% of participants in the booster dose group and 4.2% of participants in the placebo group. Most related AEs were reactogenicity events (i.e., injection site pain, fatigue, myalgia, fever and headache) and were consistent with the AE profile previously observed following 2-dose primary series of the vaccination.

Unsolicited AEs reported within 1 month following the booster dose included headache (5%), lymphadenopathy (2.8%), fever (4.8%), decreased appetite (0.2%), malaise (0.7%), nausea (0.9%) and pain in extremity (1.1%) These AEs in the vaccine group are known to be related to the vaccination and the frequency of the AEs were labelled in the Product Monograph (PM).

There were no notable patterns or numerical imbalances between treatment groups for specific categories of Serious adverse events that would suggest a causal relationship to the vaccine. No cases of vaccine-associated death, anaphylaxis, hypersensitivity, myocarditis/pericarditis, or Bell’s palsy were reported in the study. The study is ongoing and the safety data continues to be collected.

In Study C4591001, there were 684 participants 16 to17 years of age who received a booster dose of the vaccine, at least 6 months after the primary series. No new safety concerns were identified after the booster dose. A case of myocarditis was observed in a 17 year old male participant that recovered following treatment.

Very rare cases of myocarditis or pericarditis following vaccination with Comirnaty have been reported in the post-market settings. These cases occurred more commonly in adolescents and young adults. These potential safety risks are labelled in the PM and have been added to the Risk Management Plan. In addition, Health Canada and the Public Health Agency of Canada are continuously monitoring COVID-19 vaccine safety and communicate on identified new risks, if necessary.

Overall, the efficacy and safety data provided support the use of a single booster dose of Comirnaty in individuals 16 and 17 years of age.

Therefore, Comirnaty is recommend for authorization as a single booster dose in individuals 16 and 17 years of age at least six months following the primary 2-dose series.