TEL AVIV – A single shot of the Covid-19 vaccine developed by Pfizer Inc.
and BioNTech SE is 85% effective in preventing symptomatic diseases 15 to 28 days after administration, an Israeli study found, a development that could help policy makers set vaccine priorities worldwide.
Some governments are debating delaying the second shot of the recommended two-dose regimen to make the most of the vaccine shortage.
The Israeli study, conducted by the 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 as correspondence in the British medical journal Lancet, meaning it represents the authors’ views and not the journal.
The data used was collected on the 9,109 healthcare workers, who started their vaccination process on December 19.
“This is the first study to assess the effectiveness of a single dose of vaccine in real conditions and demonstrates 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 study authors.
The results of the study may differ from others because the subjects were largely younger and healthier, said Prof. Gili Regev-Yochay, one of the other authors. She also said the study could not confirm how long the single-shot protection would last, as most subjects were given a second shot.
Pfizer’s original clinical study showed 52.4% effectiveness after one injection, but it did not differentiate between before and after two weeks. That original study focused on a two-dose regimen and found 95% efficacy a week after the second shot, results similar to those of two large Israeli studies over the past few days using real-world data.
The Sheba study shows that just one dose can come close to that level of efficacy.
A table published in an online appendix to the Sheba study showed 94% effectiveness in preventing symptomatic Covid-19, 22 to 28 days after the first injection. This result was comparable to that of two previous analyzes of the Pfizer vaccine using clinical data submitted to the U.S. Food and Drug Administration.
Canadian researchers published a letter in the New England Journal of Medicine this week saying that their analysis of the data provided to the FDA found the vaccine to be 92.6% effective two weeks after the first injection. Pfizer responded in the journal that alternative dosing schedules “have not been evaluated” and that changing them is a matter for health authorities, who must monitor the changes to ensure the vaccines provide maximum protection.
An analysis of Pfizer’s clinical data published in December by Public Health England, part of the UK Department of Health and Social Care, found the vaccine to be 89% to 91% effective 15 to 28 days after the first dose.
The authors of the Sheba study said their research supported the policies of countries like the UK to delay the second dose to provide the vaccine to as many people as possible.
“This groundbreaking research supports the UK government’s decision to begin vaccinating its citizens with a single dose of the vaccine,” said Prof Arnon Afek, Deputy Director General of Sheba.
Israel leads the world in the percentage of vaccinated population. Since the program’s inception on Dec. 20, the country has delivered the first shot to about 45% of its roughly nine million people and two shots to about 30%, according to the Ministry of Health.
Israel is aiming to inoculate most of its population by March, a goal made possible after it paid a premium for Pfizer’s early deliveries and agreed to share data on its vaccine – from effectiveness to side effects. The country also placed orders with other vaccine companies, including Moderna Inc.
and AstraZeneca PLC.
Copyright © 2020 Dow Jones & Company, Inc. All rights reserved. 87990cbe856818d5eddac44c7b1cdeb8