The current Comirnaty label states that the observed risks of myocarditis and pericarditis, particularly within the first week following vaccination, are highest in males 12-17 years old and the current Spikevax label states the risks are highest in males 18-24 years old.

The new label wording proposed by the FDA for both vaccines reads: "Following administration of the 2023-2024 formula of mRNA COVID-19 vaccines, the highest estimated incidence of myocarditis and/or pericarditis was in males 16 through 25 years of age."

The FDA has also proposed the addition of new cardiovascular safety information based on the estimated incidence of post-vaccination myocarditis and/or pericarditis and one longitudinal retrospective study in hospitalized patients 5-29 years old who were diagnosed with myocarditis following vaccination.

Based on health insurance claims data, the estimated incidence of myocarditis and/or pericarditis 1-7 days post-vaccination with the 2023-2024 formulations of the COVID-19 vaccines in persons 6 months to 64 years old was 8 cases/1 million doses; the incidence was highest in males 16-25 years old (38 cases/1 million doses).1,2

In the longitudinal retrospective study, at a median of about 5 months post-vaccination with either mRNA COVID-19 vaccine, persistence of abnormal cardiac MRI findings was common, but the clinical significance of these f ndings is unknown.3