Two Canadian doctors recently made the argument that the Pfizer-BioNTech mRNA vaccine is effective enough to warrant a single-dose regimen when communities have a limited supply of the shots. Their letter, published in mid-February when Canada was experiencing a delay in vaccine shipments, states that the vaccine had an efficacy of 92.6% beginning two weeks after the first dose, and before the second was administered. The authors based their analysis on documents Pfizer submitted to the FDA.1 //

Research out of Israel published in The Lancet found that the first dose of the Pfizer COVID-19 vaccine was 85% effective two to three weeks after a single dose.3 Another study found that after one dose of the vaccine, between days 14 to 20, it offered 57% effectiveness for symptomatic COVID-19, 74% for hospitalization, and 62% for severe disease.4