TEL AVIV—A single shot of the Covid-19 vaccine developed by Pfizer Inc. and BioNTech SE is 85% effective in preventing symptomatic disease 15 to 28 days after being administered, an Israeli study found—news that could help guide policy makers setting vaccine priorities world-wide.
Some governments are debating whether to delay the second shot of the recommended two-dose regimen to make the most of the short supply of vaccines.
The Israeli study, conducted by the government-owned Sheba Medical Center and released Friday, also found a 75% reduction in all Covid-19 infections, symptomatic or asymptomatic, after the first shot. The peer-reviewed study was published in the British medical journal Lancet as a correspondence, meaning it represents the views of the authors and not the journal.
The data used was collected on the center’s 9,109 healthcare employees, who began their vaccination process starting on Dec. 19.
“This is the first study assessing effectiveness of a single vaccine dose in real-life conditions and shows early effectiveness, even before the second dose was administered,” said Prof. Eyal Leshem, director of Sheba’s Center for Travel Medicine and Tropical Diseases and one of the authors of the study.
