Single doses of the Pfizer and Moderna vaccines are more than 92 percent effective at preventing COVID-19 disease after two weeks, Canadian researchers now say.
The FDA’s own data shows that a single injection of the BioNTech-Pfizer vaccine is 92.6 percent effective after two weeks and a single Moderna shot is 92.1 percent effective, the researchers note in the New England Journal of Medicine.
Getting that second shot of the Pfizer’s vaccine increases efficacy only marginally, up to 94 percent, according to a separate study based on real-world data from Israel’s vaccination program.
And so the prescribed second doses should instead be given to those in priority groups who are still waiting for their first injection, “given the current vaccine shortage,” the researchers insist.
“With such a very protective first dose, the benefits of a scarce vaccine supply could be maximized by delaying second doses until all members of the priority group are offered at least one dose,” the researchers say in a letter to the NEJM editorial. .
“There may be uncertainty about the duration of protection with a single dose,” said the researchers.
“But the administration of a second dose within 1 month of the first, as recommended, provides little additional benefit in the short term, while high-risk individuals who could have received a first dose of that vaccine stock 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 Institut National de Sante Publique du Quebec in Quebec City.
In a letter to NEJM responding to the two researchers, Pfizer stressed that “alternative dosing regimens” have yet to be evaluated.