Risk of breakthrough infections remains very rare, three studies find

Two other studies published Wednesday also found an extremely low rate of breakthrough infections.

The first, published in JAMA Network Open, analyzed breakthrough infections among more than 5,300 vaccinated health care workers in Israel. Just 27 such infections were found. No deaths were reported, and just one patient required hospitalization. The study, however, was completed prior to the delta variant becoming the dominant strain in Israel.

The other, published in the New England Journal of Medicine, detected 94 symptomatic breakthrough infections out of more than 16,000 health care workers. That study, which ran through July, found that breakthroughs increased as the delta variant grew dominant.