Written by Deep Shukla — Fact checked by Jessica Beake, Ph.D.
A meta-analysis published in The Lancet Respiratory Medicine reports that the rate of heart inflammation after receiving a COVID-19 vaccine was comparable to that following non-COVID vaccines. Moreover, the rate of heart inflammation after COVID-19 vaccination was similar to that in the general population before the pandemic.
However, the study’s results suggest that being of the male sex, and being younger were associated with an increased risk of heart inflammation following a COVID-19 vaccine. These findings could inform public policy decisions about vaccination protocols to reduce the risk of heart inflammation in these demographics.
The study’s co-author, Dr.Kollengode Ramanathan, a cardiologist at the National University of Singapore, says:
“Our research suggests that the overall risk of myopericarditis (heart inflammation) appears to be no different for this newly approved group of vaccines against COVID- 19, compared to vaccines against other diseases.”
“The risk of such rare events should be balanced against the risk of myopericarditis from infection and these findings should bolster public confidence in the safety of COVID-19 vaccinations,” stresses Dr. Ramanathan.
Myopericarditis and vaccines
Myocarditis is a medical condition involving the inflammation of the heart muscle, while pericarditis is the inflammation of the membrane or lining that surrounds the heart. Myocarditis and pericarditis can also occur simultaneously and this condition is known as myopericarditis.
One of the common causes of myocarditis includes viral infections. For instance, studies have shown that individuals with a SARS-CoV-2 infection are at an increased risk of myocarditis and pericarditis. Myocarditis can result from the virus directly infecting the heart tissue or due to the body’s immune response to the infection.
In most cases, myocarditis following a SARS-CoV-2 infection is short-lived and resolves by itself. However, myocarditis, in rare cases, can lead to permanent heart damage, heart failure, and death.
Moreover, some studies have suggested a link between vaccination against COVID-19 with an elevated risk of myopericarditis, especially among younger males.
However, some of these studies on the adverse effects of vaccination were based on self-reports, which are susceptible to bias. In addition, the improvements in reporting of adverse events after vaccination have made it difficult to assess whether the risk of myopericarditis after receiving a COVID-19 vaccine is higher than other vaccines.
To address these issues, the present study compared the rates of myopericarditis after receiving a dose of a COVID-19 vaccine with that after non-COVID-19 vaccinations.
The study also assessed the impact of age, sex, dose, and type of COVID-19 vaccine on the risk of myopericarditis following COVID-19 vaccination.
In the present study, the researchers analyzed data on over 400 million vaccine doses accumulated from 22 studies assessing the incidence of myopericarditis after receiving a vaccine.
Specifically, the analysis included 11 studies involving over 395 million COVID-19 vaccine doses. The remaining studies involved non-COVID-19 vaccines, including smallpox (6 studies) and influenza (2 studies) vaccines.
The researchers found that the incidence rate of myopericarditis following a dose of a COVID-19 vaccine was not higher than the estimated rates of the condition in the general population before the COVID-19 pandemic.
Moreover, the rate of myopericarditis after receiving a dose of the COVID-19 vaccine was comparable to that following immunization with a non-COVID-19 vaccine. The smallpox vaccine was an exception to this trend, with a higher incidence rate of myopericarditis after a smallpox vaccine than after a COVID-19 vaccine.
The study’s authors also noted that the incidence rate of myopericarditis following COVID-19 vaccination appears to be lower than previously reported estimates of myopericarditis after a SARS-CoV-2 infection.
The researchers then assessed the impact of the type of COVID-19 vaccine, age, and sex on susceptibility to myopericarditis after receiving a COVID-19 vaccine.
They found that the number of myopericarditis cases after an mRNA COVID-19 vaccine was nearly three times higher than after a dose of a non-mRNA COVID-19 vaccine.
In addition, the risk of myocarditis was higher after the second dose of a COVID-19 vaccine than the first or the third dose.
Myopericarditis after receiving a dose of a COVID-19 vaccine was also more common in males than in females and in individuals younger than 30 years than those ages 30 and over.
Notably, the incidence rate of myopericarditis in males younger than 30 was ten times higher than in women in the same age group.
Dr. Margaret Ryan, a professor at the University of California San Diego, wrote in a commentary piece accompanying the article:
“Analyses of the pathology and immunological mechanisms behind these demographic-dependent adverse events following vaccination are likely to advance our understanding of cardiology and immunology. These advances could spur the development of safer vaccines or precision vaccination practices.”
Children not included
The study’s authors acknowledged that their study had a few limitations.
Dr. Ramanathan told MNT:
“Our findings are not generalizable to children younger than the age of 12, as there were limited data being reported on this age group. The comparisons between COVID-19 and non-COVID-19 vaccines were also made across different time periods.”
“Developments in tools (MRI, widespread echocardiography, biopsy) and improvements in vaccine surveillance systems might introduce heterogeneity and reporting in the treatment of myopericarditis,” he added.
Dr. Anders Husby, a postdoctoral researcher at Statens Serum Institut, Denmark, who was not involved in the research, told MNT, “The study is limited by the relatively few and mostly small studies of myocarditis after non-COVID-19 vaccines, why it is difficult to pinpoint the magnitude of effects of non-COVID-19 vaccines.”
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