Doubts raised over preprint study regarding myocarditis risk in teenage boys

A concerning statistic about teenagers and COVID-19 vaccines is making the rounds on social media and eliciting anxiety from parents considering whether to vaccinate their children.

"A new study from University of California found that teenage boys are more at risk from vaccines than covid; SIX times more likely to suffer from heart problems from the vaccine than be hospitalized from COVID," reads one Instagram post shared Sept. 12.

We found the "six times more likely" claim also made headlines and drew thousands of views on British news site The Telegraph, ZeroHedge.com and a site called Summit News. It caught the attention of Rep. Marjorie Taylor Greene, R-Ga., who tweeted about the study and linked to a Guardian story to support her opposition to vaccine mandates.

These posts were flagged as part of Facebook’s efforts to combat false news and misinformation on its News Feed. (Read more about our partnership with Facebook.) 

We wanted to know if the statistic had merit. But after looking into it, PolitiFact learned that the issue is far more complicated than these social media posts and headlines make it sound.

The Centers for Disease Control and Prevention is investigating cases of myocarditis in teens who received an mRNA vaccine for COVID-19. Myocarditis is defined by the Mayo Clinic as an inflammation of the heart muscle that can reduce the heart's ability to pump and cause rapid or abnormal heart rhythms. Many things can cause myocarditis, and most of these are viruses.

However, the reports spotlighting the "six times more likely" figure cite a different study that is not peer-reviewed and, despite the attention it has received on social media, has been widely criticized by researchers and physicians. They say the study used flawed methodology and drew problematic conclusions based on low-quality, raw data from the federal government’s Vaccine Adverse Event Reporting System, or VAERS.

"Many parents will see the headlines and conclude that vaccination is more dangerous than COVID, which is troubling, because that conclusion is completely unsupported by this study,"  said Johns Hopkins epidemiologist Nikolas Wada.

The study cited in these posts is titled "SARS-CoV-2 mRNA Vaccination-Associated Myocarditis in Children Ages 12-17: A Stratified National Database Analysis." It was posted Sept. 8 to MedRxiv, a site where researchers share preliminary versions of scientific papers before they are peer-reviewed or accepted for publication by a scholarly or scientific journal.

The researchers used VAERS to identify reports of 257 cardiac adverse events among vaccinated teens between Jan. 1, 2021, and June 18, 2021. The review found that for boys ages 12 to 15, the occurrence of such events was 16.2 per 100,000. For girls, the rate was much lower, at 1.3 per 100,000. 

The authors concluded that the rate of a cardiac adverse event happening post-mRNA vaccination for healthy boys is "3.7 to 6.1 times higher" than their risk of being hospitalized for COVID-19 as of Aug. 21, 2021.

Since the study was posted, however, several doctors and researchers have said that it’s findings are flawed and the conclusions people are drawing from the findings go too far. Among the concerns:

• Problematic use of VAERS data: The study relies on unvetted and low-quality data from VAERS, which helps researchers collect data on vaccine after-effects and detect patterns that may warrant a closer look.

VAERS is an open system where anyone can submit an adverse event report. These submissions are not verified, and incomplete VAERS data is often used in conjunction with false claims about vaccine safety. Health officials caution on the database itself that VAERS results are not enough to determine whether a vaccine causes a particular adverse event.

Wada said the study failed to adequately vet the data before drawing conclusions. "There was no serious clinical adjudication of suspected myocarditis cases, nor any follow-up using other data sources," he said.

• Time frame of data is inconsistent with vaccine availability for teens: The authors based the study on VAERS data for people ages 12-17 from Jan. 1 through June 18, 2021. But the vaccine didn’t become available to children ages 12-15 until May 10, and even then the only vaccine available to children in this age group was Pfizer. 

That means the study analyzed only about five weeks’ worth of data for kids younger than 16. Before May, any data detected on children would have pertained only to 16- and 17-year-olds, who were included in the original emergency use authorization given to Pfizer in December.

Dr. David Gorski, a surgery and oncology professor at Wayne State University in Detroit who writes about VAERS data, questioned this methodology. "Surely the analysis could have been carried out to a more recent date, given that VAERS is updated weekly," he wrote. 

He also took issue with the way the study characterized the data it used. The study stated that it relied on data that "included all children with at least 1 dose of any vaccination and all fully vaccinated children" (emphasis ours) — wording that gives the impression it encompasses a wide range of cases. The time frame makes clear that this was a much narrower group, eligible for only one manufacturer’s vaccine. 

• Possible authorship conflict-of-interest: One of the co-authors, Josh Stevenson, is associated with an online group called Rational Ground, which has opposed COVID-19 public health measures, including mandatory vaccinations. The group’s website describes Stevenson as a data visualization expert whose background is in computer systems engineering and consulting, with a degree in audio engineering. 

In the comments of an article about the study on ScienceBasedMedicine.org, a website that covers issues in science and medicine, the study’s lead author, Dr. Tracy Høeg, an epidemiologist who at the time of the research was affiliated with the University of California-Davis, said that the paper had no sponsorship or relationship with the group and that she had to look up what it was.

• Comparing myocarditis following vaccination to COVID-19 requiring hospitalization: Cases of myocarditis that follow vaccination are most often mild, said Dr. Frank Han, a pediatric cardiologist currently treating patients in Illinois. It can pale in comparison to what is often involved in the care and treatment of patients with COVID-19 who require hospitalization.

Whereas myocarditis patients can require overnight hospitalization for cardiac monitoring and advanced imaging, he said, "the vast majority of the patients recovered quickly and did not necessarily require the intensive monitoring."

Like adults, children with severe COVID-19 may develop respiratory failure, myocarditis, shock, acute renal failure, bleeding disorders, and multi-organ system failure, according to the CDC. Treatment for these and other severe symptoms of COVID SARS-CoV-2 can involve being placed on a ventilator.

"I have yet to witness (and have asked my colleagues too) one post-vaccine myocarditis child go on life support," Han wrote in a Twitter thread addressing the study. "Have I heard of post-#COVID19 disease children get on life support, and MISC kids go on life support? Absolutely. In the end — vaccination with COVID in those who are eligible trades in a significant risk with a much smaller risk. That's what counts in the end."

Team it's time to address the Hoeg et al preprint on post-COVID vaccine myocarditis. How am I qualified to speak about myocarditis? I am board certified in paediatric cardiology and currently have patients recovering from this condition. TLDR: They are doing quite well. #MRI

— Frank Han (@han_francis) September 10, 2021

In response to questions from PolitiFact about the six-fold figure, Høeg said she and the other authors specifically looked at 120-day COVID-19 hospitalizations rates, not overall infection hospitalization rates, and "compared those with post-dose 2 vaccination myocarditis rates in boys that were reported in the VAERS registry system."

"The figures you cite," Høeg wrote in an email, "were specifically for boys 12-15 without medical comorbidities using the hospitalization data we had from mid-August, but the national pediatric hospitalization rates have continued to go up from that time."

That means that the "six times higher" figure is lower now and no longer accurate, she said, but was at the time of the analysis. 

The study’s takeaway, Høeg said, should be that there is a "specific concern about post-vaccination myocarditis in boys that needs to be studied further."

The CDC in July released information based on its own analysis of reports involving myocarditis among people who received an mRNA COVID-19 vaccine.

Using VAERS data that had been vetted and confirmed, it determined that there may be a link between myocarditis and vaccination, particularly among boys. This association is apparent in the CDC’s report as well as in data from Israel, experts told us, and more rigorous study is needed.

The CDC study estimated that for every million second doses of vaccine administered to boys ages 12 to 17, vaccination would prevent, on average, 5,700 COVID-19 cases, 215 COVID-19 hospitalizations, 71 ICU admissions, and two deaths. By comparison, there would be an expected 56 to 69 cases of myocarditis. The risks were found to be significantly lower for girls. 

Meanwhile, public health officials have also said that COVID-19 infections alone commonly lead to instances of myocarditis and pericarditis and that, in those cases, damage to the heart is frequently severe.

"The CDC continues to recommend that children aged 12 years and older get vaccinated for COVID-19," CDC spokesperson Martha Sharan said. "The known risks of COVID-19 illness and its related, possibly severe complications, such as long-term health problems, hospitalization, and even death, far outweigh the potential risks of having a rare adverse reaction to vaccination, including the possible risk of myocarditis or pericarditis."

The CDC’s findings are currently under review at a peer-reviewed journal and include reports of adverse events that have been verified to meet the agency’s working definition for myocarditis or myopericarditis, Sharan said. The agency did this, in part, by interviewing doctors involved in the patients’ care and reviewing medical records associated with these reports.

CLARIFICATION (Sept. 23, 2021): This story has been updated to reflect that Dr. Høeg's residency with the University of California-Davis is no longer active. She was affiliated with the institution at the time of the study.