Regulatory Decision Summary for Comirnaty

To support authorization of the Cominarty booster dose, immune response and safety data (cut-off date of 2021-06-17) from a subset of subjects of the ongoing study C4591001, who received a booster dose of 30 µg Cominarty approximately 6 months after the second dose of Cominarty, were provided. Eligible, male or female adult participants who completed the two-dose series were allowed to enroll to receive a booster dose. In total, 306 individuals 18 to 55 years of age received a 30 µg Comirnaty booster dose in this portion of the study.

Noninferiority of immune responses 1 month after a Comirnaty booster dose compared to 1 month after completion of the primary 2-dose series was assessed in subjects who had no evidence of past SARS-CoV-2 infection up to 1 month after the booster vaccination. Overall, the findings were that the antibody levels were 3-fold higher after the booster dose relative to levels after the second dose.

At the time of analysis, participants were followed-up for safety for 1 month after receiving the booster. Safety and immune response data from 6-months and 18-months of follow-up will be provided to Health Canada when available. The number of participants with any adverse events (AE) was 44/306 (14.4%). No AE leading to withdrawal were reported and no study participants died. The most common AEs (occurring in over 10% of subjects) included injection site pain (83.0%), fatigue (63.7%), headache (48.4%), chills (29.1%), muscle pain (39.1%), and joint pain (25.3%).

No cases of severe allergic reaction (anaphylaxis), blood clotting events, nerve-related events (Bells palsy, Guillain-Barre Syndrome [GBS]), or heart-related events (myocarditis/pericarditis) were reported.

The exact timing of the booster doses and appropriate populations to administer booster doses will depend on a variety of factors including the local epidemiological contexts which are continually evolving and may vary between provinces and territories. As such, standardized timing is not currently recommended and the decision for when and for whom to implement a booster dose should be made considering relevant vaccine effectiveness data (e.g. evidence of waning effectiveness) taking into account the available safety and immune response data.

Based on the totality of the information, the benefit-risk profile for a 30 µg booster dose of Comirnaty is considered favourable in individuals 18 years of age or older. The safety and immune response of a booster dose of Comirnaty in individuals 55 years of age and older were extrapolated from safety and immune response data in the younger adult population (55 years of age or less).