Israel's Health Ministry said on Sunday it is examining a small number of cases of heart inflammation in people who had received Pfizer's COVID-19 vaccine, though it has not yet drawn any conclusions.

First day of vaccinating medical staff at Sourasky Medical Center in Tel Aviv with Pfizer COVID-19 vaccine on December 20, 2020. Photo: VCG

Pfizer said it has not observed a higher rate of the condition than would normally be expected in the general population. Israel's pandemic response coordinator, Nachman Ash, said that a preliminary study showed "tens of incidents" of myocarditis occurring among more than 5 million vaccinated people, primarily after the second dose.

Ash said it was unclear whether this was unusually high and whether it was connected to the vaccine. 

Most of the cases were reported among people up to age 30. "The Health Ministry is currently examining whether there is an excess in morbidity [disease rate] and whether it can be attributed to the vaccines," Ash said. Ash, who spoke about the issue in a radio interview and during a news conference, referred to it as a "question mark," and emphasized that the Health Ministry has yet to draw any conclusions.

Determining a link, he said, would be difficult because myocarditis, a condition that often goes away without complications, can be caused by a variety of viruses and a similar number of cases were reported.