Published in the Journal of the American College of Cardiology, the study found that although cases were rare, men under the age of 40 were at the highest risk of developing heart complications such as myocarditis and pericarditis, which usually occurred within 21 days a second . vaccination dose. Myocarditis refers to the inflammation of the heart muscle, while pericarditis is the inflammation of the outer lining of the heart. “Few population-based analyzes have been conducted to directly compare the safety of the two mRNA COVID-19 vaccines, which differ in important ways that could affect safety,” the study’s lead author, a Centers for Disease Control epidemiologist in British Columbia Dr. Naveed Janjua. , he said in a press release. The study followed people 18 years and older who received a second dose of either the Pfizer BioNTech or Moderna Spikevax COVID-19 vaccines in British Columbia between January 1, 2021, and September 9, 2021. In total, more than 2.2 million Pfizer second doses were administered in the p .X. 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 the rate of heart inflammation and found that there were 35.6 cases per million for Moderna and 12.6 per million for Pfizer – a nearly threefold difference. Rates for myocarditis were higher with the Moderna vaccine in both men and women between the ages of 18 and 39, with even higher rates seen in men 18 to 29. By comparison, rates of myocarditis in the general population in 2018 were 2.01 to 2.2 per million people, according to the study. In addition to being an uncommon but worrisome side effect of 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 is seven times higher with a COVID-19 infection than with a vaccine dose. From December 2021 to April 2022, Canadian soccer star Alphonso Davies was sidelined with myocarditis after a bout of COVID-19. Dr. Janjua is also the executive director of data and analytical services at the British Columbia Center for Disease Control and a clinical professor in the department of population and public health at the University of British Columbia. He says the finding should help direct which populations receive which vaccine to maximize benefits while minimizing adverse effects. “Our findings have implications for mRNA vaccine development strategy, which should also take into account the self-limiting and mild nature of most myocarditis events, the benefits provided by vaccination, the higher efficacy of Moderna’s vaccine against infections and nursing. [found in prior studies]and the apparent higher risk of myocarditis after infection with COVID-19 than with mRNA vaccination,” explained Janjua. A limitation of the study is that it was observational, meaning it did not prove that the vaccination caused myocarditis or pericarditis. Also, relying on hospital and emergency department data, the study may have missed some less severe cases. In an editorial commenting on the study, Israel-based cardiologists Drs. Guy Wittberg and Dr. Ilan Richter wrote that the results are “reassuring about the safety of the vaccine and should help eliminate vaccination reluctance caused by concerns about cardiac adverse events. Such a conclusion is based not only on the proven efficacy of vaccines, but also on data showing that infection with COVID-19 is associated with a much higher risk of myocarditis.” More than 93 million doses of COVID-19 vaccine have been administered in Canada, including nearly 62 million Pfizer vaccines and more than 28 million Moderna vaccines. Both companies are committed to studying the long-term effects of vaccine-related heart problems. A January 2022 study found the U.S. rate of myocarditis was 52.4 and 56.3 per million for Pfizer and Moderna in young men aged 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 certain age groups. According to the Public Health Service of Canada, myocarditis and pericarditis remain rare complications. The agency urges anyone experiencing chest pain or pressure, irregular heartbeat or shortness of breath after vaccination to seek medical help. He says cases appear to occur most among teenagers and young adult males after a second dose and within seven days of vaccination. “In most cases, someone who has had myocarditis or pericarditis after an mRNA vaccine should delay getting another dose,” the agency says. “The rates of these conditions after the booster dose with an mRNA vaccine appear to be somewhat lower than after the second dose.”
