https://mobile.reuters.com/article/amp/idUSKBN2AI0EC
(Reuters) - The second dose of Pfizer Inc's COVID-19 vaccine could be delayed in order to cover all priority groups as the first one is highly protective, two Canada-based researchers said in a letter published in the New England Journal of Medicine.
The vaccine had an efficacy of 92.6% after the first dose, Danuta Skowronski and Gaston De Serres said, based on an analysis of the documents submitted by the drugmaker to the U.S. Food and Drug Administration (FDA).
These findings were similar to the first-dose efficacy of 92.1% reported for Moderna Inc's mRNA-1273 vaccine, according to the letter here on Wednesday.
........
In Britain, authorities have said that data supported its decision to move to a 12-week dosing schedule for Pfizer's COVID vaccine.
PS
the published paper
Safety and Efficacy of the BNT162b2 mRNA Covid-19 Vaccine
https://www.nejm.org/doi/full/10.1056/NEJMc2036242
.....
Even before the second dose, BNT162b2 was highly efficacious, with a vaccine efficacy of 92.6%, a finding similar to the first-dose efficacy of 92.1% reported for the mRNA-1273 vaccine (Moderna).3
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, but the administration of a second dose within 1 month after the first, as recommended, provides little added benefit in the short term, while high-risk persons who could have received a first dose with that vaccine supply are left completely unprotected. Given the current vaccine shortage, postponement of the second dose is a matter of national security that, if ignored, will certainly result in thousands of Covid-19–related hospitalizations and deaths this winter in the United States — hospitalizations and deaths that would have been prevented with a first dose of vaccine.