Israeli study finds Pfizer vaccine 85% effective after first shot

Researchers say a longer follow-up is required to understand the effect of one shot to inform second dose delay policy.

A new study on healthcare workers in Israel has found that one shot of a two-dose vaccine produced by Pfizer-BioNTech is 85 percent effective, heightening the debate over the possibility of spacing out doses. The Lancet medical journal published on Thursday the results of the study based on more than 9,000 health care workers from the Sheba Medical Center, an Israeli research hospital, showing a drop by 85 percent of staff presenting COVID-19 symptoms after a period of 15 to 28 days after the first dose. The overall reduction of infections, including asymptomatic cases detected by testing, was 75 percent.