Polack et al. (Dec. 31)1 report a vaccine efficacy of 94.8% against Covid-19 after two doses of the messenger RNA (mRNA) vaccine BNT162b2 (Pfizer–BioNTech).
The authors also report a vaccine efficacy of 52.4% from after the first dose to before the second dose, but in their calculation, they included data that were collect-ed during the first 2 weeks after the first dose, when immunity would have still been mounting.
We used documents submitted to the Food and Drug Administration2 to derive the vaccine efficacy beginning from 2 weeks after the first dose to before the second dose (Table 1).
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% report-ed for the mRNA-1273 vaccine (Moderna).
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.
