Novavax COVID-19 Vaccine Associated With Heart Inflammation: Study

Syringes with a shot of Novavax's COVID-19 vaccine in Berlin, Germany, on Feb. 28, 2022. Carsten Koall/Getty Images

A higher-than-expected number of heart inflammation cases have occurred in people who received Novavax’s COVID-19 vaccine, researchers reported in a new study.

Sixty-one cases of myocarditis, pericarditis, or both following a Novavax vaccination were reported in the World Health Organization’s vaccine safety database through Aug. 23, 2022, Spanish researchers found.

Using pre-pandemic rates of heart inflammation in the population, the researchers calculated that the number of postvaccination cases was higher than expected.

Reporting odds ratio values of higher than one indicate a higher-than-expected rate. For myocarditis following the Novavax vaccination, the ratio was 5.2. For pericarditis, it was 24.75. For myopericarditis, or both conditions at once, it was 14.4.

Heart inflammation is a known side effect of the Pfizer and Moderna COVID-19 vaccines, which utilize messenger RNA (mRNA) technology, but little data has been collected on the condition following the Novavax vaccination, which doesn’t contain mRNA.

The U.S. Food and Drug Administration, when it authorized Novavax’s shot last summer, noted in fact sheets that clinical trials indicate there are increased risks of myocarditis and pericarditis after receipt of the Novavax vaccine. In the trial data submitted to the regulator, five cases of one or both conditions were reported in the vaccinated and zero were reported in placebo recipients. U.S. authorities have since cleared a Novavax booster and recently reached a deal to obtain up to 1.5 million additional doses on top of the original tranche.

The European Medicines Agency initially didn’t warn about inflammation after the administration of the Novavax vaccination but later added a warning to its product information.

Fifty cases of myocarditis, pericarditis, or myopericarditis after Novavax vaccination have been reported in Australia, according to the new study. Two have been reported in the United States and nine have been reported in Europe. Most have been among those aged 18 to 44.

While the exact mechanism for induction of myocarditis has yet to be confirmed, the study’s authors pointed out that the Pfizer, Moderna, and Novavax vaccines use nanoparticles to deliver a spike protein into the body.

“More research would be needed to understand the role of nanoparticles in the potential risk of vaccine-induced myocarditis,” they wrote.

The researchers, who also detected a higher-than-expected number of reports for the Pfizer and Moderna vaccines, said that health care professionals should be aware that Novavax may cause myocarditis, pericarditis, or both.

The study was funded by CIBERSAM, a research network, and was published in Drugs—Real World Outcomes on Feb. 14.

Novavax said in 2022, based on its interpretation of all of its clinical trials, that there was “insufficient evidence to establish a causal relationship” between the vaccine and the inflammation.

In an emailed statement in response to a request for comment on the new study, the company wrote: “Reports of myocarditis or pericarditis after Nuvaxovid vaccination are rare. While the risk of developing myocarditis or pericarditis is very low, both are important identified risks of COVID-19 vaccines, including Nuvaxovid.”

Nuvaxovid is the trade name for the company’s vaccine.

The company also claimed that the reports of inflammation “have generally been mild, self-limited, and clinically consistent with the literature describing myocarditis after mRNA COVID-19 vaccination.” A number of postvaccination cases among those who received the Pfizer or Moderna vaccine weren’t resolved months later, and some have ended in death.

Guidance

Some experts warn against getting one of the vaccines if a person has a history of myocarditis or pericarditis, or develops it after vaccination.

“Development of myocarditis or pericarditis after a dose of an mRNA COVID-19 vaccine (i.e., Moderna or Pfizer-BioNTech) or Novavax COVID-19 Vaccine is a precaution to a subsequent dose of any COVID-19 vaccine and subsequent doses should generally be avoided,” the U.S. Centers for Disease Control and Prevention states on its website.

Australian authorities claim that people who experienced myocarditis or pericarditis “can receive a COVID-19 vaccine” but advise consulting an expert “about the best timing of vaccination and whether any additional precautions are recommended.”

The regulator notes that some vaccine-induced myocarditis cases have led to death.

Some people who suffered from heart inflammation after a shot have gone on to get another one, according to case reports.

Two cases outlined in a paper by Australian doctors described a 26-year-old healthy male who experienced pericarditis after a second dose of Pfizer’s vaccine. The symptoms went away. Six months later, he received a booster produced by Novavax. He was diagnosed with pericarditis after experiencing similar symptoms, including chest pain.

A 25-year-old female, meanwhile, presented with chest pain and other issues 48 hours after receiving a second dose of Pfizer’s vaccine. The woman, diagnosed with myopericarditis, experienced “persistent symptoms” that required returning to the hospital multiple times over five months.

Symptoms eventually went away and abnormalities seemed to disappear. The woman then took a booster of Novavax’s vaccine. Five days later, she experienced chest pain and similar symptoms. She was diagnosed with myocarditis. The symptoms persisted two months post-vaccination, with no end in sight.