Pfizer-BioNTech’s Covid-19 vaccine has been linked to an increased risk of myocarditis, an inflammation of the heart muscle, confirms a major new study from Israel. But the side effect remains rare, and Covid-19 is more likely to cause myocarditis than the vaccine, scientists reported Wednesday.
The research, based on the electronic health records of around two million people aged 16 and over, provides a comprehensive insight into the real frequency of various adverse events, both after vaccination and after infection with the coronavirus.
Although the study didn’t break down myocarditis risks by age or gender, the mean age of people who developed the disease after vaccination was 25 years, and 19 of the 21 cases were male, the researchers reported.
In addition to myocarditis, the Pfizer vaccine was also linked to an increased risk of swollen lymph nodes, appendicitis, and shingles, although all three side effects remained rare in the study. Coronavirus infection was not linked to these side effects, but it increased the chances of several potentially serious cardiovascular problems, including heart attacks and blood clots.
“Coronavirus is very dangerous and in many ways very dangerous to the human body,” said Ben Reis, co-author of the new study and director of the predictive medicine group at Boston Children’s Hospital Computational Health Informatics Program.
He added, “If the reason someone has been reluctant to vaccinate is because of fear of this very rare and usually not very serious adverse event called myocarditis, this study shows that this very same adverse event is actually associated with a higher risk, if you are not vaccinated and are infected. “
The data came amid an intense discussion between federal agencies about the risks of myocarditis and pericarditis, an inflammation of the lining of the heart, among younger recipients of both Pfizer BioNTech and Moderna vaccines, which very likely led to concerns about the Food and Drug Administration to negotiate larger pediatric trials with vaccine manufacturers this summer in the hopes of properly assessing the risks before a possible emergency approval for younger children. The companies are investigating lower doses in children to reduce some of the risk.
In their review of the Pfizer BioNTech vaccine, regulators paid close attention to an American health claims database that found that the risk of the disease in 16- and 17-year-old boys vaccinated could be as high as 1 in 5,000. The cases in the database are unconfirmed, the FDA warned in an analysis released this week, but they were viewed as a reasonable estimate of the potential risk. Even in the worst-case scenarios of post-vaccination myocarditis and pericarditis modeled by the FDA, the benefits of vaccination outweighed the risks, according to the analysis.
The study was one reason the FDA said this week that after the vaccine from Pfizer-BioNTech is approved, Pfizer will conduct studies on myocarditis and pericarditis risks in people who received the vaccination, including long-term results for those who did get sick after vaccination.
Israel’s vaccination campaign, based on the Pfizer vaccine, got off to a quick start; By May 24, nearly five million people, or about 55 percent of the country’s population, had received both doses of the vaccine.
The new study, published in the New England Journal of Medicine, is based on an analysis of electronic health records from Clalit Health Services, the country’s largest HMO
Aug. 25, 2021, 7:39 a.m. ET
The researchers put together a group of about 880,000 people aged 16 and over who were vaccinated by May 24th. To form a control group, they assigned each of these individuals to an unvaccinated individual who was medically and demographically similar.
“You can think of them as pseudo-twins,” said Dr. Ran Balicer, Chief Innovation Officer of Clalit Health Services and lead author of the new study.
Then the researchers calculated the frequency of 25 different possible adverse events in each group. In a second round of analysis, they calculated the frequency of the same potential side effects in a group of 170,000 people who tested positive for the coronavirus and in a similar group of uninfected controls.
They found that myocarditis, while rare, was more common in the vaccinated group than the unvaccinated group. The researchers found that there were 2.7 additional cases of myocarditis for every 100,000 people in the vaccinated group compared to the unvaccinated group.
Understand US vaccination and mask requirements
- Vaccination rules. On August 23, the Food and Drug Administration fully approved Pfizer-BioNTech’s coronavirus vaccine for people aged 16 and over, paving the way for increased mandates in both the public and private sectors. Private companies are increasingly demanding vaccines for employees. Such mandates are legally permissible and have been confirmed in legal challenges.
- Mask rules. The Centers for Disease Control and Prevention in July recommended that all Americans, regardless of vaccination status, wear masks in public places indoors in areas with outbreaks, reversing the guidelines offered in May. See where the CDC guidelines would apply and where states have implemented their own mask guidelines. The battle over masks is controversial in some states, with some local leaders defying state bans.
- College and Universities. More than 400 colleges and universities require a vaccination against Covid-19. Almost all of them are in states that voted for President Biden.
- schools. Both California and New York City have introduced vaccination mandates for educational staff. A survey published in August found that many American parents of school-age children are against mandatory vaccines for students but are more likely to support masking requirements for students, teachers and staff who are not vaccinated.
- Hospitals and medical centers. Many hospitals and large health systems require their employees to have a Covid-19 vaccine, due to rising case numbers due to the Delta variant and persistently low vaccination rates in their communities, even within their workforce.
- New York City. Proof of vaccination is required by workers and customers for indoor dining, gyms, performances, and other indoor situations, though enforcement doesn’t begin until September 13th. Teachers and other educational workers in the city’s vast school system are required to have at least one vaccine dose by September 27, without the option of weekly testing. City hospital staff must also be vaccinated or have weekly tests. Similar rules apply to employees in New York State.
- At the federal level. The Pentagon announced that it would make coronavirus vaccinations compulsory for the country’s 1.3 million active soldiers “by mid-September at the latest. President Biden announced that all civil federal employees would need to be vaccinated against the coronavirus or undergo regular tests, social distancing, mask requirements and travel restrictions.
But the risks were even higher for those who contracted the virus. For every 100,000 people infected with the coronavirus, there were 11 additional cases of the disease compared to those who hadn’t.
The study provides a critical context for understanding the risks and benefits of vaccination, said Dr. Brian Feingold, an expert on childhood heart inflammation at UPMC Children’s Hospital in Pittsburgh, who said he takes calls from parents who are concerned about the risk of myocarditis.
“And nobody blows that away, but I think you just have to see it in context,” he said. “These risks associated with Covid are higher than the risks associated with the vaccine.”
In addition to myocarditis, coronavirus infection was also linked to an increased risk of heart attacks, irregular heartbeat, blood clots in the lungs or legs, kidney damage, and bleeding inside the skull. For example, for every 100,000 infections there were an additional 25 heart attacks and 62 cases of blood clots in the lungs.
“When trying to make your decision on whether or not to take the vaccine, you need to ask yourself not only what potential side effects are associated with taking the vaccine, but what I am risking thinking of Covid – 19 as another option, ”said Dr. Balicer.
While the study is reassuring, it’s important to keep collecting data on myocarditis risks, especially in young men, scientists said.
“But we are in this scorching hot moment,” said Dr. Sean O’Leary, a pediatric infectious disease expert at the University of Colorado’s Anschutz Medical Campus. “That’s what we have, and the benefits still seem to far outweigh the risks.”
In a recent study, which has not yet been published in a peer-reviewed journal, the researchers calculated that 12- to 17-year-old boys were about six times more likely to develop myocarditis after being infected with the virus than after receiving one of the mRNA vaccinations.