Single doses of Pfizer and Moderna vaccines are more than 92% effective in preventing COVID-19 disease after two weeks, say Canadian researchers.
The FDA’s own data show that a single shot of the BioNTech-Pfizer vaccine is 92.6 percent effective after two weeks, and a single Moderna jab is 92.1 percent effective, the researchers note in the New England Journal of Medicine.
Obtaining the second photo of the Pfizer vaccine increases the effectiveness only marginally, up to 94%, according to a separate study based on real-world data from Israel’s vaccination program.
Therefore, the second prescribed dose should be given instead to those in the priority groups who are still waiting for their first shot, “given the current lack of vaccine,” the researchers ask.
“With such a highly protective first dose, the benefits of a small amount of vaccine could be maximized by postponing the second dose until all members of the priority group are given at least one dose,” the researchers said in a letter. addressed to NEJM publishers.
There may be uncertainty about the duration of single-dose protection, the researchers said.
But taking the second dose within a month of the first, as recommended, offers few added benefits in the short term, while people at high risk who might have received a first dose with that source of vaccine are left completely unprotected. ”
The letter was written by Dr. Danuta M. Skowronski of the British Columbia Center for Disease Control in Vancouver and Dr. Gaston De Serres of the Quebec National Institute of Public Health in Quebec City.
In a letter to the NEJM responding to the two researchers, Pfizer stressed that “alternative dosing regimens” have yet to be evaluated.