80% risk reduction for asymptomatic people after taking Covid-19 vaccine

A new study has revealed that 10 days after receiving the second dose of an mRNA Covid-19 vaccine, asymptomatic patients are far less likely to test positive, compared to patients who have not been vaccinated for the coronavirus.

With two doses of a messenger RNA Covid-19 vaccine, people with no symptoms showed an 80 per cent lower adjusted risk of testing positive for the coronavirus.

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The study, published in the journal Clinical Infectious Diseases, has been carried out by researchers at Mayo Clinic.

The authors stated that these findings underscore the efficacy of messenger RNA vaccines for Covid-19 to significantly limit the spread of the virus by asymptomatic people, who may unknowingly spread the infection to others.

Study design

The researchers carried out a retrospective study of 39,000 patients who underwent pre-procedural molecular screening tests for Covid-19.

More than 48,000 screening tests were performed, including 3,000 on patients who had received at least one dose of a messenger RNA Covid-19 vaccine.

These screening tests were part of the routine Covid-19 testing prior to treatments not related to the infection, such as surgeries and other procedures.

Patients in the vaccinated group had received at least one dose of a messenger RNA Covid-19 vaccine.

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Key findings

The researchers found that asymptomatic patients receiving at least one dose of the mRNA Covid-19 vaccine, 10 days or more prior to screening, were 72 per cent less likely to test positive, while those receiving two doses were 73 per cent less likely, compared to the non-vaccinated group.

After adjusting for a range of factors, researchers found an 80 per cent risk reduction of testing positive for Covid-19 among those with two doses of a messenger RNA Covid-19 vaccine.