Mayo Clinic determines mRNA COVID-19 vaccines greatly reduce risks of asymptomatic infection, spread

In a study funded by the Mayo Clinic and published in the journal Clinical Infectious Diseases last week, researchers determined that after two doses of mRNA vaccines for COVID-19, asymptomatic patients are less likely to be infected and unknowingly spread the virus.

After two doses of mRNA COVID-19 vaccines, participants in the study with no symptoms showed an 80 percent lower adjusted risk of testing positive for COVID-19 thereafter. Conducted among a selection of 39,000 patients who underwent pre-procedural molecular screening tests for COVID-19, the research lasted from Dec. 17, 2020, to Feb. 8, 2021, at Mayo Clinic facilities in Minnesota, Arizona, and Wisconsin.

“We found that those patients without symptoms receiving at least one dose of the first authorized mRNA COVID-19 vaccine, Pfizer-BioNTech, 10 days or more prior to screening were 72% less likely to test positive,” Dr. Aaron Tande, Mayo Clinic infectious diseases specialist and co-first author of the paper, said. “Those receiving two doses were 73% less likely, compared to the unvaccinated group.”

Both the Pfizer/BioNTech and Modern vaccines are mRNA vaccines currently authorized for emergency use in the U.S. The authors state that the findings of these tests stressed the success of such vaccines in limiting the spread of COVID-19 even among those with no symptoms.

The study included 3,000 screening tests conducted on patients who had already received at least one dose of an mRNA COVID-19 vaccine before the experiment began.