Canadian researchers are now saying that single doses of Pfizer and Moderna Vaccines are almost 92% effective in preventing the illness after two weeks. The researchers note in the New England Journal of Medicine shows a single injection of the Moderna is 92.1% effective. The FDA also claims that a single shot of BioNTech-Pfizer is 92.6% effective in preventing contamination after two weeks.
According to a separate study based on Israel’s vaccination program’s real-world data, the efficacy only increases marginally to 94% after the second Pfizer shot. Given the current vaccine shortage, researchers urge the authorities to prescribe the second dose to those on the waiting list for the first shot.
The researchers say in a letter to the NEJM editors, “With such a highly protective first dose, the benefits derived from a scarce supply of vaccine could be maximized by deferring second doses until all priority group members are offered at least one dose. There may be uncertainty about the duration of protection with a single dose.”
Even with the administered duration of one month between the doses of the vaccine, there is only limited added benefit. However, the other high-risk people without the first dose are left wholly unprotected.
Dr. Danuta M. Skowronski of the British Columbia Centre for Disease Control in Vancouver and Dr. Gaston De Serres of the Institut National de Sante Publique du Quebec in Quebec City wrote the letter. As a response to both the researchers, Pfizer stressed that “alternative dosing regimens still need to be evaluated.