Pfizer's jab ups heart inflammation risk, with threat higher among Covid-19 patients: Study

JERUSALEM • The use of Pfizer and German partner BioNTech's Covid-19 vaccine marginally increases the risk of heart inflammation, but the risk is higher among those infected with the coronavirus, a study showed.

Among every 100,000 patients who get the vaccine, one to five will likely develop myocarditis who would not otherwise have developed it, researchers reported in the New England Journal of Medicine based on data from Clalit Health Services, an Israeli health maintenance organisation.

That rate is much higher - 11 per 100,000 - among people infected with the coronavirus, they said.

The data comes after Pfizer-BioNTech's Covid-19 vaccine became the first fully approved vaccine in the United States for people aged 16 and older, a move that could potentially persuade vaccine sceptics to get the shot.

Researchers compared adverse event rates in 884,828 vaccinated individuals and an equal number of unvaccinated people. Overall, 21 people reported myocarditis in the vaccinated group - mostly young men - compared with six people among the unvaccinated.

Most adverse events in vaccinated people were mild, but some, such as myocarditis, are potentially serious, researchers said.

The researchers also analysed adverse event rates in more than 240,000 infected patients. The results indicate Covid-19 infection is itself a very strong risk factor for myocarditis, and it also substantially increases the risk of other serious adverse events, they said.

"This is a really terrific paper in part because it takes data from the same system, and tries to provide more information, not just about the potential risks of vaccination, but also the potential benefits of vaccination," said Dr Grace Lee of Stanford University, whose editorial was published with the report.

Israel's Health Ministry said in June that it saw a possible link between such cases and Pfizer's Covid-19 vaccine.

REUTERS