The use of Pfizer and German partner BioNTech's widely used Covid-19 vaccine marginally increases the risk of heart inflammation, but the risk is higher among those infected with the coronavirus, a study published in the New England Journal of Medicine shows.

Among every 100,000 patients who get the vaccine, 1 to 5 will likely develop myocarditis who would not otherwise have developed it, researchers reported based on data from Clalit Health Services, a large Israeli health management organisation.

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

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