Single doses of the 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 shows that a single injection of the BioNTech-Pfizer vaccine is 92.6 percent effective after two weeks, and a single Modern injection is 92.1 percent effective, the researchers note in the New England Journal of Medicine.
Taking the second injection of the Pfizer vaccine increases effectiveness only marginally, to 94 percent, according to a separate study based on real-world data from Israel’s vaccination program.
And so the second prescribed doses should be administered to those in priority groups who are still waiting for their first injection, “given the current shortage of vaccine,” the researchers insist.
“With this first highly protective dose, the benefits derived from a scarce supply of vaccine could be maximized by postponing second doses until all members of the priority group receive at least one dose,” say the researchers in a letter to the editors of NEJM .
“There may be uncertainty about the duration of protection with a single dose,” said the researchers.
“But administering a second dose within 1 month of the first, as recommended, offers little additional benefit in the short term, while high-risk people who could have received a first dose with this vaccine supply are left completely unprotected” .
The letter was written by Dr. Danuta M. Skowronski of the British Columbia Disease Control Center 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 emphasized that “alternative dosing regimes” still need to be evaluated.