COVID-19 vaccines may be associated with a heightened risk of myopericarditis among men, according to a new analysis published in the American Journal of Cardiology.
However, the authors emphasized, the benefits of being vaccinated still outweigh this “very small” risk.
“A number of case reports and series have recently been published describing patients who experienced myocarditis after receiving the COVID-19 vaccination,” wrote first author Rosemary Farahmand, MD, of Harvard Medical School, and colleagues. “However, it is uncertain if these cases may have been secondary to other etiologies of myocarditis like viruses, drugs, or autoimmune conditions, and only coincidentally occurred after COVID-19 vaccination. It is also unclear if the incidence of myocarditis observed is different than expected.”
Hoping to gain a better understanding of these relationships, Farahmand et al. tracked data from more than 268,000 adults who received at least one dose of a COVID-19 vaccine in the state of Massachusetts from August 2020 to May 2021. The study’s control group was made up of 235,000 of the same patients—from 2018 and 2019, well before they had received any doses of a COVID-19 vaccine.
The researchers focused on the electronic health records of each patient, looking for any changes in health or healthcare utilization after various COVID-19 surges and after vaccination.
Overall, the group identified 12 cases of myopericarditis in vaccinated study participants. Three of those cases came after the first dose of a COVID-19 vaccine, seven cases came after the second dose and the other two cases came after a single-dose vaccine. Meanwhile, there were five cases of myopericarditis reported in the control group.
The age-adjusted incidence rate of myopericarditis among men was higher in the vaccinated group than in the study’s control group. This was not, however, the case among women.
“Previous research has demonstrated that there are slightly higher rates of myopericarditis of any cause in men than in women,” the authors wrote. “One proposed potential mechanism for this difference in incidence is that the higher levels of estradiol in women may confer a cardioprotective effect. If COVID-19 vaccination is a causative factor in the development of myopericarditis in some people, the same mechanisms may be making men more susceptible than women after COVID-19 vaccination.”
The team did note that this was not a randomized controlled trial. Also, using study subjects as their own controls likely kept selection bias to a minimum, but it does mean that all patients were two years old after they had been vaccinated.
Even with these limitations in mind, the authors said their work “reaffirms the apparent increase in the diagnosis of myopericarditis in men (particularly aged 25 to 44 years) after COVID-19 vaccination.”
They concluded, however, by highlighting the continued importance of these vaccines.
“The benefits of COVID-19 vaccination to individual and public health outweigh the very small risks of myopericarditis diagnosed after vaccination,” they concluded.
Read the full analysis here.
Michael has more than 16 years of experience as a professional writer and editor. He has written at length about cardiology, radiology, artificial intelligence and other key healthcare topics.