Now We Know: Covid-19 Vaccines Prevent Asymptomatic Infection, Too
The CDC has now confirmed what we have hoped for: the mRNA vaccines made by Pfizer and Moderna are highly effective at preventing SARS-CoV-2 infection in real world conditions. It was known previously from clinical trials that these vaccines were effective at preventing symptomatic disease. What was not known was whether they prevented asymptomatic infection.
Here is how the CDC reached this conclusion. Beginning in mid-December 2020, 3,950 people employed in frontline health care professions (e.g. physicians, nurses, and first responders) in eight US locations were tested each week for 13 weeks to