The health ministry of Israel has identified less than 10 cases of heart inflammation following a third dose of the Pfizer (NYSE:PFE)/BioNtech (Nasdaq:BNTX) COVID-19 vaccine, Reuters news agency reported on Friday.

In data published late on Thursday, the health ministry reported nine cases of myocarditis within four age groups that comprised more than 1.5 million people who had received a booster shot.

All were male, three were between the ages of 16 and 29 and six were in the 30-59 group. Eight more possible cases were still being reviewed. Most myocarditis cases are generally mild, the health ministry said.

In total, out of all 3.2 million Israelis who have received a third jab, 25 reported serious adverse events that appeared within 30 days of the shot, including myocarditis, though a causal link had yet to be established among many of them.

Israel began administering boosters to risk groups in July and later expanded its campaign to include anyone over the age of 12, five months or more after a second dose.