A dose of the Pfizer-BioNTech vaccine is administered in Cwmbran, Wales.Credit: Matthew Horwood/Getty
2 March — Just one dose of vaccine protects against silent COVID infection
Asymptomatic coronavirus infections were four times less frequent in health-care workers who had received a single dose of a prominent COVID-19 vaccine than in their unvaccinated counterparts.
Michael Weekes at the University of Cambridge, UK, and his colleagues analysed the results of almost 8,900 SARS-CoV-2 tests taken by UK health-care workers without symptoms of COVID-19 (M. Weekes et al. Preprint at Authorea https://doi.org/fxkd; 2021). Study participants who were tested at least 12 days after receiving one dose of the vaccine developed by Pfizer of New York City and BioNTech of Mainz, Germany, had an infection rate of only 0.2%. By contrast, unvaccinated participants had an infection rate of 0.8%.
The team also noted that participants who showed evidence of SARS-CoV-2 infection well after vaccination tended to have lower levels of the coronavirus in their bodies than did those who were infected and unvaccinated, although the result did not reach statistical significance. If corroborated, this would suggest that the few vaccinated health-care workers who do have an asymptomatic infection are less likely to infect other people than are unvaccinated workers who become infected.
The findings have not yet been peer reviewed.
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