A complete vaccination reduces the risk of coronavirus infection by about 90%, according to a study of nurses, firefighters and other frontline workers in the United States, who were immunized with an mRNA-based vaccine.
Clinical trials have shown that mRNA-based vaccines made by Moderna and Pfizer - BioNTech are highly effective in protecting people against diseases caused by SARS-CoV-2.
To find out if vaccines also protect people being infected, they studied the results of the SARS-CoV-2 test of nearly 4,000 people on the front lines who are at high risk. The work was done by Mark Thompson and his colleagues at the US Centers for Disease Control and Prevention in Atlanta, Georgia.
Study participants were vaccinated between mid-December 2020 and mid-March 2021.
After vaccination, they wiped their own noses for viral testing once a week for 13 weeks.
Participants were considered fully immunized two weeks after receiving the second dose of the vaccine.
Complete immunization was 90% effective in protecting people infections and a single dose was 80% effective.
But the researchers warn that since few participants were infected after vaccination, it is difficult to say with high precision the effectiveness of vaccines against infection.