COVID-19 vaccine coverage in health-care workers in England and effectiveness of BNT162b2 mRNA vaccine against infection (SIREN): a prospective, multicentre, cohort study
Study (n=23 324) reported that a single dose of BNT162b2 (Pfizer) vaccine, as compared to an unvaccinated cohort, showed vaccine effectiveness of 70% 21 days after first dose and 85% 7 days after two doses in the study population which was exposed to the dominant variant B1.1.7.
Source:
The Lancet
SPS commentary:
A related commentary notes that most epidemiologists think the threshold to achieve herd immunity is about 70% protected by vaccination or previous infection. Based on the above results, to achieve this in the absence of naturally acquired immunity, nearly 100% of the population would need to be vaccinated with one dose or about 80% with two doses