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Evaluating the CDC ACIP’s Response to Covid Vaccine-Associated Myocarditis

A pediatrician and internal medicine physician weighs in on a recently identified vaccine side-effect.

Bo Stapler, MD
Published in
5 min readJun 24, 2021


Today the U.S. Department of Health and Human Services, the Centers for Disease Control and Prevention (CDC), and 15 other medical organizations** who form the CDC’s Advisory Committee on Immunization Practices (ACIP) issued a statement supporting Covid vaccination despite new data suggesting an association of myocarditis and pericarditis with vaccine administration. Here’s what they had to say, and here’s why I’m glad they said it:

The ACIP did not hide or inappropriately minimize the fact that vaccine reporting systems like VAERS and v-safe have revealed an association of myocarditis and pericarditis with the Pfizer-BioNTech and Moderna Covid vaccines — two of the three vaccines approved by the Federal Drug Administration (FDA) for emergency use to prevent Covid-19. Before I go further, some background on myocarditis and pericarditis:

Myocarditis is an inflammation of the heart muscle that can be triggered by a number of factors including viral infections and even malfunctions of the body’s own immune system. Myocarditis is a rare complication of infection with influenza virus as well as other viruses including SARS-CoV-2, the virus that causes Covid-19. Most of the time myocarditis resolves either on its own or with medical treatment. In some cases, however, it can lead to long-term adverse effects on the heart, and very rarely, it can result in death.

Pericarditis is another type of inflammation near the heart. Except instead of the heart muscle becoming inflamed, pericarditis is an inflammation of a thin sack or lining that surrounds the heart. Pericarditis also typically resolves on its own or with medical, or sometimes even surgical, treatment. In very rare instances, pericarditis can result in death or become chronic or recurrent which can result in significant morbidity for a patient suffering from this condition.

Among 300 million vaccine doses administered in the U.S., approximately 1200 preliminary reports of either myocarditis or pericarditis have been issued. This equates to about four per million vaccine recipients.

Digging a little deeper into the data, we find that the demographic at highest risk for vaccine-related myocarditis are boys ages 12 to 17. Of note, this same group is one of the lowest risk groups for complications of infection from SARS-CoV-2. The CDC estimates that for every one million boys in this age group who receive their second vaccine dose, 5,700 cases, 215 hospitalizations, and two deaths from Covid-19 are subsequently prevented. They also estimate that 56 to 69 individuals per million in this demographic may experience myocarditis as a side effect of the vaccine.

The authors of the ACIP statement put into words what can be gleaned from statistics such as these. They explain that myocarditis and pericarditis are “extremely rare side effect[s], and only an exceedingly small number of people will experience it after vaccination.” At the same time, their comments provide reassurance that “most cases are mild, and individuals recover often on their own or with minimal treatment.”

Furthermore, the statement addresses the issue of evaluating risk which remains a key driver in regards to decision-making during the pandemic. The authors make the important distinction between the risk of vaccination and the risk of Covid-19 infection by commenting, “We know that myocarditis and pericarditis are much more common if you get Covid-19, and the risks to the heart from Covid-19 infection can be more severe…the risks of being unvaccinated are far greater than any rare side effects from the vaccines.”

As its name Centers for Disease Control and Prevention implies, the CDC is not the Center for Providing Simple Practical Guidance to Reduce Disease Somewhat. Their expressed purpose is to control and prevent disease whether it’s convenient for everyone or not. Not surprisingly, some have questioned the practicality and timeliness of the CDC’s guidance at times during the pandemic. Fortunately, this statement strikes a commendable balance by providing truthful, understandable information to the public without raising unnecessary alarm.

This circumstance is yet another example of vaccine reporting systems successfully working as designed to pinpoint small signals among the noise so that medical experts can recognize when vaccine recipients are experiencing symptoms at a frequency that exceeds what would be predicted by random occurrences. Such reporting systems also identified a rare, but serious, side effect of the Janssen Covid-19 Vaccine (Johnson & Johnson) referred to as vaccine-induced immune thrombotic thrombocytopenia (VITT). Product information for the Janssen vaccine now contains a warning regarding VITT particularly in the demographic of females aged 18 to 49 in which this complication is most frequently observed. Likewise, it is anticipated that the FDA will soon add information about myocarditis and pericarditis to the information sheets for the Pfizer-BioNTech and Moderna vaccines.

Historically, the field of medicine has been far from perfect when it comes to safety. For example, until about 120 years ago, the chance of surviving a surgical procedure was less than that of dying during the procedure or shortly thereafter as a result of a surgical complication. Medical providers aren’t perfect either. As a physician, I have experienced some proud moments as well as some that I’m not so proud of.

The suffering that healthcare providers, their patients, and their loved ones have endured at the hands of this virus is almost unimaginable. At the same time, the Covid vaccine movement and the relief it has provided is an astounding and almost unimaginable achievement for medicine and humankind. Witnessing this growing movement, especially the moments when honesty and transparency prevail, make me proud to work in healthcare and hopeful for its future.

** The statement was co-signed by the U.S. Department of Health and Human Services (HHS), Centers for Disease Control and Prevention (CDC), American Academy of Family Physicians (AAFP), American Academy of Pediatrics (AAP), American College of Obstetricians and Gynecologists (ACOG), American College of Physicians (ACP), American Heart Association, American Hospital Association (AHA), American Medical Association (AMA), American Nurses Association (ANA), American Public Health Association (APHA), Association of Public Health Laboratories, Association of State and Territorial Health Officials (ASTHO), Big Cities Health Coalition, Council of State and Territorial Epidemiologists, Infectious Diseases Society of America, and National Association of County and City Health Officials (NACCHO)

Dr. Stapler practices adult and pediatric hospital medicine in Billings, Montana, USA, and loves every minute of it (usually). Check out more of his work and follow him at



Bo Stapler, MD

Health & science writer on Elemental & other pubs. Hospitalist physician in internal medicine & pediatrics. Interpreter of medical jargon.