John R. Su, Michael M. McNeil, Kerry J. Welsh, Paige L. Marquez, Carmen Ng, Ming Yan, Maria V. Cano

Abstract

Background: Myopericarditis after vaccination has been sporadically reported in the medical literature. Here, we present a thorough descriptive analysis of reports to a national passive vaccine safety surveillance system (VAERS) of myopericarditis after vaccines licensed for use in the United States.

Methods: We identified U.S. reports of myopericarditis received by VAERS during 1990–2018 that met a published case definition for myopericarditis or were physician-diagnosed. We stratified analysis by age group (<19, 19–49, ≥50 years), describing reports by serious/non-serious status, sex, time to symptom onset after vaccination, vaccine(s) administered, and exposure to other known causes of myopericarditis. We used Empirical Bayesian data mining to detect disproportionate reporting of myopericarditis after vaccination.

Results: VAERS received 620,195 reports during 1990–2018: 708 (0.1%) met the case definition or were physician-diagnosed as myopericarditis. Most (79%) myopericarditis reports described males; 69% were serious; 72% had symptom onset ≤ 2 weeks postvaccination. Overall, smallpox (59%) and anthrax (23%) vaccines were most commonly reported. By age, among persons aged < 19 years, Haemophilus influenzae type b (22, 22%) and hepatitis B (18, 18%); among persons aged 19–49 years smallpox (387, 79%); among persons aged ≥ 50 years inactivated influenza (31, 36%) and live attenuated zoster (19, 22%) vaccines were most commonly reported. The vaccines most commonly reported remained unchanged when excluding 138 reports describing other known causes of myopericarditis. Data mining revealed disproportionate reporting of myopericarditis only after smallpox vaccine.

Conclusions: Despite the introduction of new vaccines over the years, myopericarditis remains rarely reported after vaccines licensed for use in the United States. In this analysis, myopericarditis was most commonly reported after smallpox vaccine, and less commonly after other vaccines.

Summary

I presented a patient with a history of myopericarditis. While I was familiar with myocarditis and pericarditis, I was not previously familiar with myopericarditis. Upon my initial search there were a lot of recently published articles about myopericarditis in young adults and adolescents after COVID vaccines. I wanted to find an article that discussed potential adverse affect in adults and came across this article. While there have been reports of association, no causality has been established between vaccines, specifically smallpox vaccine, and myopericarditis. This article from Vaccine used over 620,000 reports of patients, 708 of which had myopericarditis, and broken down by age, gender, type of vaccine, and other potential causes of the disease in order to identify a association between vaccines, or specific type of vaccine, and myopericarditis. Time to symptoms onset was <14 days between vaccine and myopericarditis, median reported age 24 years, majority were males. Most frequently reported vaccines among all ages were smallpox, anthrax, and typhoid. Those <18 years most frequent reported vaccines were Haemophilus influenza b and hepatitis B. Those 19-49 most common was smallpox. Ages 50+ was seasonal influenza and live attenuated zoster. Distribution based on sex was similar to past reporting with majority of cases being male, about 57%. Also, majority of patients were <55 years. It is currently unknown why the differences between sex and age occur. Higher proportion of reported myopericarditis was seen after smallpox vaccine which likely reflects an association between the two, with similar rates seen in ages 19-31 in military population (prior studies) and general population. Overall myopericarditis was a rarely reported adverse effect from vaccines (0.1% of adverse effects reported during analysis period) and while surveillance for myopericarditis after vaccination is warranted the analysis did not reveal any new or unexpected safety concerns.