Of particular interest were events of myocarditis and pericarditis. Postmarketing data from individuals receiving mRNA vaccines have demonstrated increased risks of myocarditis and pericarditis, particularly within 7 days following the second primary series dose. The observed risk has been highest in adolescent and young adult males.
Available data from short-term follow-up suggest that most individuals have had resolution of symptoms, although information is not yet available about potential long-term sequelae.
The Spike protein antigen can induce antibodies to SARS-CoV-2 spike glycoproteins that cross-react with myocardial contractile proteins, including myocardial alpha-myosin heavy chain ( Vojdani and Kharrazian, 2020 ).
It has been postulated that the effect of these antibodies, influenced by hormonal differences, immune-genetic background, age, and sex are potential mechanisms of myocardial injury associated with SARS-CoV-2 infection or COVID-19 vaccination ( Heymans and Cooper, 2022 ).
Over the course of the clinical development program, events of myocarditis and pericarditis were identified from in multiple studies, as well as from the adolescent expansion substudy and booster dose substudy of 301.
Therefore, an evaluation of cases of myocarditis and pericarditis was undertaken, incorporating data from across the clinical development program to provide the most robust assessment.
In summary, the events of myocarditis / pericarditis are concerning for a causal association with Nuvaxovid ( NVX-CoV2373; Novavax ) for the following reasons: 1) five events were reported within 2 weeks of vaccination, 2) only 1 event had a clearly identified alternative etiology ( COVID-19 ) strongly associated with myocarditis, and other events had only circumstantial evidence of potentially plausible alternative etiologies, and 3) four of the events occurred in young men, a subject population known to be at higher risk for mRNA COVID-19 vaccine-associated myocarditis.
Additionally, identification of multiple potential vaccine-associated cases in a premarket safety database of approximately 40,000 vaccine recipients raises concern that if causally associated, the risk of myocarditis following Nuvaxovid could be higher than reported during post-authorization use of mRNA COVID-19 vaccines ( for which no cases were identified in pre-authorization evaluation ). ( Xagena )
Source: FDA, 2022