mRNA vaccines cut risk of asymptomatic COVID-19

Ten days after receiving a second dose of the messenger RNA (mRNA) vaccines from Pfizer/BioNTech or Moderna, people without COVID-19 symptoms are far less likely to be carrying the virus and unknowingly spreading it, compared with people who have not been vaccinated, according to Mayo Clinic doctors.

Their data, published on Wednesday in Clinical Infectious Diseases, come from 39,000 patients who were routinely tested for COVID-19 before undergoing various medical procedures.

More than 48,000 screening tests were performed, including 3,000 on patients who had received at least one dose of an mRNA vaccine. Among individuals who had received a single dose of vaccine at least 10 days earlier, they saw a 72% reduction in the risk of a positive COVID-19 test.

After adjusting for a range of factors, they found an 80% risk reduction of testing positive for COVID-19 among people without symptoms who had gotten both doses.

The authors said their findings underscore the fact that messenger RNA vaccines for COVID-19 can help to significantly limit the spread of the virus by people without symptoms.