The risk of developing heart disease is two to three times higher with the Moderna COVID-19 vaccine than with Pfizer, according to a new Canadian study.
Published in the Journal of the American College of Cardiology, the study found that although cases are rare, men under 40 have the highest risk of heart complications such as myocarditis and pericarditis. , usually appearing within 21 days after a second. vaccination dose.
Myocarditis refers to inflammation of the heart muscle, while pericarditis is an inflammation of the outer lining of the heart.
“Several population-based analyzes have been performed to directly compare the safety of two COVID-19 mRNA vaccines, which differ in important points that could affect safety,” the authors wrote. lead study, British Columbia Center for Disease Control epidemiologist Dr Naveed Janjua said in a press release.
The study followed people 18 years and older who received a second dose of the COVID-19 vaccine Pfizer BioNTech or Moderna Spievax in British Columbia between January 1, 2021 and September 9, 2021. plus, more than 2.2 million second doses of Pfizer were administered in BC during that time, plus 870,000 doses of Moderna.
Within 21 days of the second dose, there were 59 cases of myocarditis (28 Pfizer and 31 Moderna) and 41 cases of pericarditis (21 Pfizer and 20 Moderna). The researchers then calculated rates of heart inflammation and found there were 35.6 cases per million for Moderna and 12.6 per million for Pfizer — a nearly threefold difference. The incidence of myocarditis was higher with the Moderna vaccine in both men and women between the ages of 18 and 39, with rates even higher in men between 18 and 29. For comparison, rates The prevalence of myocarditis in the general population in 2018 was 2.01 to 2.2 per million people, according to the study.
In addition to being an uncommon but worrisome side effect for mRNA vaccines, myocarditis has also been linked to viral infections such as COVID-19 and influenza. A recent study found that the risk of developing myocarditis in people with COVID-19 was seven times higher than the vaccine dose. From December 2021 to April 2022, Canadian soccer star Alphonso Davies was sidelined with myocarditis following an episode of COVID-19.
Dr. Janjua is also executive director of data and analytics services at the British Columbia Center for Disease Control and a clinical professor in the University of British Columbia’s department of population and public health. This finding will help guide which populations receive which vaccines to maximize benefits while minimizing adverse effects, he said.
“Our findings have implications for the strategic planning of mRNA vaccine deployment, should also consider the self-limited and mild nature of most cases of myocarditis, the benefits of vaccination carry. In contrast, the higher efficacy of the Moderna vaccine for infection and hospitalization [found in prior studies]and the risk of myocarditis was clearly higher after infection with COVID-19 than with mRNA vaccination,” explains Janjua.
One limitation of the study is that it was observational, which means it did not prove vaccination caused myocarditis or pericarditis. Additionally, by relying on hospital and emergency department data, the study may have missed some less severe cases.
In an editorial commentary on the study, Israeli cardiologists Dr Guy Witberg and Dr Ilan Richter wrote that the results “reconcile the safety of the vaccine and will help put an end to the situation.” ‘hesitancy to vaccinate’ due to concerns about adverse effects on the heart; such a conclusion is based not only on the proven efficacy of the vaccine but also on data showing COVID-19 infection is associated with a much higher risk of myocarditis.”
More than 93 million doses of the COVID-19 vaccine have been administered in Canada, including nearly 62 million doses of Pfizer and more than 28 million doses of Moderna. Both companies have committed to studying the long-term effects of vaccine-related heart problems.
A January 2022 study found rates of myocarditis in the United States to be 52.4 and 56.3 per million for Pfizer and Moderna in young men ages 18 to 24. In June, the US Centers for Disease Control and Prevention warned that the Moderna vaccine may cause a higher risk of myocarditis in some age groups.
According to Public Health Canada, myocarditis and pericarditis remain rare complications. The agency urges anyone who experiences chest pain or tightness, irregular heartbeat or difficulty breathing after receiving a vaccine to seek medical care. It said cases appeared to occur most in adolescents and young adults, men, after the second dose and within seven days of vaccination.
“In most cases, a person who has developed myocarditis or pericarditis after receiving an mRNA vaccine should postpone another dose,” the agency said. “The incidence of these conditions after the booster dose with the mRNA vaccine appears to be slightly lower than after the second dose.”