All patients have recovered spontaneously and within a short period, which makes milder patients less likely to self-report, de Lemos said. And so, there is very limited data in people who have milder symptoms, as they may not seek medical help, Simon added.

Current data hinges on people who report symptoms, such as severe chest discomfort and shortness of breath and thus go to the hospital, Kim noted. The second knowledge gap is how many people have had milder forms of heart inflammation with the second shot. SARS-CoV-2 enters lung cells via the ACE2 receptor.

It is possible that the SARS-CoV-2 spike protein antigen produced by the mRNA vaccines binds to the ACE2 receptors in the heart, which leads to the side effect, he noted. It is possible that the mRNA vaccines’ lipid nanoparticle vector is also a contributor to the hypersensitive reaction, he added.īut there is also real-world evidence showing people who do have this side effect do not have an inflammatory storm, meaning there could be a more specific side-effect mechanism, de Lemos said. This aligns with the fact that younger people generally have a more exuberant immune system response, de Lemos noted. The leading hypothesis to the cause of heart inflammation is the immune system’s immunologic reaction to the vaccine, said Dr Erin Simon, emergency medicine physician, Cleveland Clinic Akron General, Ohio. But there are still many knowledge gaps to make more definitive conclusions, such as a clear consensus as to the cause of this side effect, and how many people have had milder forms of this issue, experts said. Using mRNA vaccines as a booster may lead to more acute heart inflammation in people who have had milder forms of these side effects after the second dose, Kim added. Myocarditis is an inflammation of the heart muscle and pericarditis is an inflammation of the lining that surrounds the heart. Also, these side effects were primarily observed in younger men, particularly in the 16–39-year-old age group. It is possible that in people who received a different technology for their first dose, and then switched to an mRNA vaccine for their second dose, these people could also experience heart inflammation issues, though more data is needed, de Lemos noted.Īccording to a 10 June CDC presentation detailing US vaccine safety data collected through 31 May, most heart inflammation events were observed after the second dose (573 events) compared with the first dose (216 events). This suggests that myocarditis following mRNA vaccination requires an initial exposure, either from COVID-19 infection itself or from the first dose of an mRNA vaccine, he added. In people who have experienced myocarditis after the first dose, they appear to have previously had COVID-19 infection, Kim noted.

Heart inflammation is mainly observed after the second dose, agreed Dr Han Woong Kim, associate professor of medicine, Department of Cardiology, Duke University School of Medicine, Durham, North Carolina. The risk of myocarditis and pericarditis with mRNA vaccine boosters needs to be monitored closely as it is possible the third dose may lead to an increased frequency of these rare side effects, said Dr James de Lemos, professor of internal medicine, Division of Cardiology, University of Texas Southwestern Medical Center, Dallas. Heart inflammation seen with prior exposure AstraZeneca, Johnson & Johnson and Moderna did not reply to a comment request. A Pfizer spokesperson said it will continue to monitor all Comirnaty (BNT162b2) adverse events from clinical trials and from real-world experience.

Side effect of covid booster