An update on myocarditis cases

Myocarditis (or “inflammation of the heart”) came to the forefront on May 23, when the CDC started investigating several cases following vaccination with Pfizer. At the time there were 89 cases reported to VAERS, 14 cases among people who were vaccinated through the U.S. military health system, and 62 cases in Israel. For more detail on these cases, see my previous post here. Briefly, the majority of patients were younger (<30 years) males. There were two associated deaths (in Israel).

On May 24, the VaST (COVID-19 Vaccine Safety Technical) Work Group at the CDC concluded that a “higher number of observed than expected myocarditis/pericarditis cases in 16- to 24-year-olds" occurred and “analyses suggest that these data need to be carefully followed”. Basically we needed more data and more detail about these cases.

So, where are we now?

Last week, during an FDA meeting on pediatric COVID vaccines, Dr. Tom Shimabukuro (the Deputy Director of the Vaccine Task Force at the CDC) provided an update.

There are now 475 cases of myocarditis following vaccination among people <30 years old in the United States. Among the 475 patients, 60% (or 285 cases) had been fully investigated. Among the 285 cases…

  • 81% had full recovery of symptoms

  • 19% had ongoing signs or symptoms or unknown status

    • At the time, 15 were still hospitalized (3 were in the ICU)

The American Academy of Pediatrics recently released a pre-print describing 7 of these patients.

Is this higher than the background (expected) rate?

To determine causality, one key answer we need is: Is the rate of myocarditis after vaccination higher than the rate of myocarditis in the general population? If it is, then myocarditis may be due to the mRNA vaccine.

  • Among 18-24 year olds, we expected around 8-83 cases of myocarditis per million in the general population. After the vaccine, though, the rate was 196 cases per million.

  • Among 16-17 year olds, we expected 2-19 cases per million. After vaccination, the rate was 79 per million.

So, yes, myocarditis following vaccination (and particularly the second dose) continues to be higher than expected among the younger population.

Where are we with the Israel cases?

Out of >5 million people vaccinated, Israel has seen 275 cases of myocarditis. Among these cases:

  • Majority spent no more than 4 days in the hospital

  • 95% of cases were classified as mild

  • Most common among men ages 16 to 19

  • More common after the second dose

Israel health authorities stated: “There is a probable link between receiving the second dose (of Pfizer) vaccine and the appearance of myocarditis among men aged 16 to 30". Nonetheless, Israel concluded that the benefits outweigh the risks and has continued to vaccinate 12+ year olds with Pfizer.

Next steps in the U.S.?
There are still a lot of unanswered questions:

  1. What are the outcomes for the other 40% of cases still under investigation?

  2. Do the benefits outweigh the risks in the U.S.? We know there’s a link between COVID19 disease and heart injury (herehere, and here).

  3. What is the biological plausibility? In other words, how can the vaccine biologically cause myocarditis, especially focused in men?

  4. Is this consistently happening in other countries? We know the answer for Israel. Europe is also investigating cases of myocarditis and they should have their report done by July.

All of these questions will be discussed in grave detail this Friday, June 18 at the ACIP advisory meeting. It starts at 11am EST; here is the agenda.

I will be there and, as always, will provide cliff notes immediately following. Should be an informative (and fascinating) discussion.

Love, YLE

Symptoms of myocarditis are: chest pain, shortness of breath, or palpitations. In most cases, patients responded well to medications and rest, and their symptoms improved quickly. Here is more detailed information on the CDC website.