Myopericarditis after COVID-19 vaccination is rare, international study finds

The overall risk of myopericarditis after COVID-19 vaccination is very low, affecting 18 people per million doses of vaccine. A new study published in Respiratory Medicine The Lancetconfirms that this risk is comparable or lower after COVID-19 vaccination compared to other non-COVID-19 vaccines.

The researchers looked at international databases, looking at more than 400 million vaccination doses, to compare the risk of myopericarditis after vaccination against COVID-19 and other diseases such as influenza and smallpox. They found no statistically significant difference between the incidence of myopericarditis after COVID-19 vaccination (18 cases per million doses) and other vaccinations (56 cases per million doses).

“Our research suggests that the overall risk of myopericarditis does not appear to be different for this group of newly approved vaccines against COVID-19, compared to vaccines against other diseases. The risk of such rare events must be weighed against the risk of myopericarditis due to infection. and these findings should build public confidence in the safety of COVID-19 vaccinations,” says Dr. Kollengode Ramanathan, Cardiac Intensivist at National University Hospital Singapore and corresponding author.

Myopericarditis is a condition that causes inflammation of the heart muscle and, in some cases, serious permanent heart damage. It is most often caused by viruses but can also occur after vaccination in rare cases. Cases of myopericarditis have been reported following mRNA-based COVID-19 vaccination, particularly in adolescents and young adults. This study aimed to determine whether this increase in reporting was due to a true increase in incidence or the result of improved reporting systems and recall bias.

The researchers analyzed more than 20 studies from international databases with reported incidences of myopericarditis after any type of vaccination between January 1947 and December 2021. Of these, 11 studies focused specifically on COVID-19 vaccinations, covering more than 395 million doses of COVID-19 vaccine, or nearly 300 million of them were mRNA vaccines. The rest of the studies looked at other vaccinations such as smallpox (2.9 million doses), influenza (1.5 million doses) and others (5.5 million doses).

The rate of myopericarditis after COVID-19 vaccination was 18 cases per million doses. For all other viral vaccinations combined, the rate of myopericarditis was 56 cases per million doses.

Among COVID-19 vaccinations, the risk of myopericarditis was higher for those who received mRNA vaccines (22.6 cases per million doses) compared to non-mRNA vaccines (7.9 cases per million doses). Reported cases were also higher in people younger than 30 (40.9 cases per million doses), men (23 cases per million doses) and after the second dose of COVID-19 vaccine (31.1 cases per million doses).

To put the findings in context with the risk of myopericarditis following COVID-19 infection, the authors conducted a post-study analysis. Among the 2.5 million patients hospitalized with COVID-19, many of whom had clinical or radiological suspicion of myopericarditis, 1.1% had myopericarditis. However, while these numbers provide a frame of reference, the authors note that the results are not directly comparable with the number of myopericarditis cases following COVID-19 vaccination due to different units of measurement.

“The occurrence of myopericarditis after non-COVID-19 vaccination might suggest that myopericarditis is a side effect of inflammatory processes induced by any vaccination and is not unique to SARS-CoV-2 spike proteins in vaccines or COVID-19 infection,” says Dr Jyoti Somani, infectious disease specialist at National University Hospital Singapore and co-author “It also underscores that the risks of such infrequent adverse events should be outweighed by the benefits of vaccination, which include lower risk of infection, hospitalization, severe illness and death from COVID-19. »

The authors acknowledge some limitations to this study, noting in particular that the results include only a small proportion of children under the age of 12 who have only recently been eligible for vaccination, and that the results of this study cannot be generalized to this age group. In addition, comparisons were made over different time periods for different vaccines. Diagnostic tools may differ or not be available, leading to decreased case reporting in earlier studies.

In a linked comment, Margaret Ryan of the Defense Health Agency and clinical professor at the University of California, San Diego, USA, who was not involved in the study, said: “Reports of unexpected adverse events, albeit rare and limited to a select subset of vaccinees – have the potential to damage confidence in the vaccine at a critical time in the pandemic response Like Ling and colleagues, all professionals who have described myocarditis after COVID-19 vaccination emphasized that the benefits of vaccination far outweigh the risks amid the current pandemic. Nevertheless, scientific knowledge and public health strategies must continue to evolve. Alternative vaccine platforms, vaccine doses, or vaccine schedules may reduce the risk of rare adverse events after vaccination and should be explored in the context of changing infection risk.

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