First Dose of Pfizer Vaccine Gives About 50% COVID Protection, Not 91% as claimed

The NEJM paper actually states that the efficacy between the first and second doses was found to be 52 percent when given 21 days apart. After the second dose, the efficacy raises to 95 percent.

A spokesperson at Pfizer has responded to the call for the aggressive roll out the first dose. "As has been previously reported and published in The New England Journal of Medicine, the final primary efficacy analysis of our ongoing Phase 3 clinical study demonstrated a vaccine efficacy rate of 95 per cent in participants, from 7 days after the second dose.

Although some protection from the vaccine appears to begin after the first dose (52 per cent), the information for healthcare professionals approved by the UK regulator (the MHRA) states that, individuals may not be protected until at least 7 days after their second dose of the same vaccine. Two doses of the vaccine 21 days apart are required to provide the maximum protection and this correlates with the level of neutralising antibodies."

The study's authors noted, however, that it was not "designed to assess the efficacy of a single-dose regimen".

According to preliminary data from Israel's mass vaccination program as reported by Newsweek, the Pfizer vaccine reduces the risk of infection by around 50 percent 14 days after the first of two shots is administered.