Israeli researchers have claimed that Pfizer’s COVID-19 vaccine marginally increases the risk of ‘myocarditis,’ inflammation of the heart muscle. However, the risk of myocarditis is much higher among those infected with COVID-19.
The new real-world study has been conducted by the Clalit Health Services (CHS), Israel’s largest state-mandated healthcare provider, and got recently published in the New England Journal of Medicine.
Over the course of the study, CHS researchers analyzed the electronic health records of over 2 million individuals- both vaccinated and unvaccinated- to look for adverse events after both vaccination and COVID-19 diagnosis.
Of the 884,828 vaccinated individuals, 21- most of them young males- developed myocarditis after receiving Pfizer’s vaccine. On the other hand, only 6 unvaccinated individuals developed myocarditis.
The researchers also analyzed the adverse events among 240,000 individuals infected with Coronavirus. They found COVID-19 to be a strong risk factor of myocarditis which increases the risk of other serious adverse events.
CHS researchers claimed that 1 to 5 individuals per 100,000 will likely experience myocarditis after receiving the Pfizer vaccine while 11 individuals per 100,000 will likely develop myocarditis after getting infected with COVID-19.
Note that Israel mostly relied on Pfizer’s vaccine in its vaccination campaign. By the end of May this year, more than five million people, or 55% of the country’s population, had already received both doses of the vaccine.
This year in June, Israeli researchers had first claimed that Pfizer’s COVID-19 vaccine was associated with hundreds of cases of myocarditis in the country following the commencement of the mass vaccination drive in December 2020.