Regulatory Decision Summary for Comirnaty

To support authorization of the Comirnaty booster dose, the immune response and safety data were provided from a subset of subjects from an ongoing study in children 5 to <12 years of age evaluating the safety, tolerability, and immunogenicity of the Comirnaty vaccine. These subjects received a booster dose of 10 µg of Comirnaty approximately 6 months after the second dose of Comirnaty.

The immune response one month after a Comirnaty booster dose compared to one 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 one month after the booster vaccination. Overall, the antibody levels were 2.17-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 12-months of follow-up will be provided to Health Canada when available. The number of participants with any Adverse Events (AE) was 36/401 (9.0%). No AE or serious AEs leading to withdrawal from the study were reported and no study participants died. The most common AE after Dose 3 included pain at the injection (73.9%), fatigue (45.6%), headache (34.0%), myalgia (18.3%), chills (10.5%), injection site redness (15.6%), and swelling (16.4%). These AEs were similar to what was reported following the primary series. The most frequently reported unsolicited adverse event was lymphadenopathy (2.5%) which was reported at a higher frequency compared to the primary series (0.9%) but with similar onset timing, severity levels, and duration.

At the time of analysis, there were no AEs of clinical interest reported of anaphylaxis, myocarditis, pericarditis, Bell’s palsy (or facial paralysis/paresis), or appendicitis. No cases of arthritis, thrombocytopenic events, thromboembolic or intravascular coagulation events, autoimmune or demyelination events, meningitis, encephalitis, neuritis, peripheral neuropathy, vasculitis, Kawasaki disease, MIS-C, or acute respiratory distress syndrome were reported following Dose 3 in this population.

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. 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 10 µg booster dose of Comirnaty is considered favourable in individuals 5 through <12 years of age.

For further details about Comirnaty, please refer to the Product Monograph, approved by Health Canada and available through the Drug Product Database.