Messenger RNA vaccines reduce risk of asymptomatic infection, study finds

Participants who received two doses of a COVID-19 messenger RNA vaccine were 80% less likely to test positive for asymptomatic SARS-CoV-2, according to the results of a real-world study published in Clinical infectious diseases.

Even after one dose, the risk of asymptomatic infection was reduced by 79%, the researchers reported. The two messenger RNA vaccines authorized in the United States are manufactured by Pfizer-BioNTech and Moderna.

“As people receive their routine care and care for their patients, if they have a pre-procedure testing protocol like we do, they can be reassured that these vaccines will reduce the risk of infection for. these patients, “ Aaron J. Tande, MD, consultant in the division of infectious diseases and associate professor of medicine at Mayo Clinic College of Medicine, Healio said.

“For the broader COVID-19 landscape, we think a good proportion – some studies have estimated 50% of infections – come from asymptomatic or presymptomatic people. This suggests that vaccines not only prevent serious illnesses, but can also prevent further transmission from people. [who] are asymptomatic because they are simply less likely to be infected, ”Tande said.

Tande and colleagues performed a retrospective cohort study of asymptomatic adult patients who underwent a total of 48,333 pre-procedural screening tests for SARS-CoV-2 from December 17, 2020 to February 8, 2021. They analyzed the RR of ‘a positive SARS-CoV. -2 test in asymptomatic people who received one dose of vaccine compared to those who had not yet been vaccinated.

A positive SARS-CoV-2 test result was identified in 42 (1.4%) of 3006 tests administered to vaccinated patients and 1436 (3.2%) of 45327 tests administered to unvaccinated patients (RR = 0 , 44; 95% CI, 0.33-0.6). The risk of asymptomatic SARS-CoV-2 infection was lower in individuals more than 10 days after their first dose (RR = 0.21; 95% CI 0.12-0.37) and greater than 0 days after their second dose (RR = 0.2; 95% CI, 0.09-0.44) compared to unvaccinated individuals.

Tande said more studies are needed to address reducing the spread of COVID-19 after vaccination over longer periods of time.

“We need to get larger studies to confirm this and look at specific subgroups of patients. Do people who are immunocompromised have the same results? Tande said.

ADD A SUBJECT TO EMAIL ALERTS

Receive an email when new articles are posted on

Please provide your email address to receive an email when new articles are posted on .

“data-action =” subscribe “> Subscribe

We have not been able to process your request. Please try again later. If you continue to experience this problem, please contact [email protected].

Back to Healio

COVID-19 Resource Center