According to the Heroes-Recover study funded by the US CDC, mRNA vaccines Pfizer-BioNtech and Moderna reduce the risk of infection with the coronavirus SARS-COV-2 by 91% in fully vaccinated people. This study also shows that mRNA vaccination makes symptoms milder and shorter for people with certain vaccines who contract COVID-19. The study also shows that people who have been vaccinated but are infected are less likely to spread the virus than those who are not.
The first results of the HEROES-RECOVER study, led by Arizona State University, were published last March. They were enriched with 4 additional weeks of data and confirmed previously observed trends.
In the new analysis, 3,975 participants, mostly caregivers or workers who are more likely to be exposed to the virus because of their occupation, for SARS-CoV-2 for 17 consecutive weeks (from December 13, 2020 to December 10, 2020) was tested weekly. April 2021) at eight US sites. Participants themselves collected nasal swabs that were laboratory tested for SARS-CoV-2. If the tests were positive, the samples were subjected to further testing to determine the amount of detectable virus in the nose and the number of days after the test came back positive.
Participants were followed over time and data were analyzed according to vaccination status. To assess the benefits of the vaccine, the study researchers took into account the spread of the SARS-CoV-2 virus in the area and the frequency of use of personal protective equipment (PPE).
After full vaccination (14 days or more after the second dose), the participants’ risk of infection was reduced by 91%. After partial vaccination (14 days or more from 1 to 13 days after dose 2), the participants’ risk of infection was reduced by 81%. These estimates include symptomatic and asymptomatic infections.
Another lesson is that people who were fully or partially vaccinated developed COVID-19, spending an average of six days less sick and two days less in bed. They had a nearly 60% lower risk of developing symptoms such as fever or chills, compared to those without vaccination. Some study participants infected with SARS-CoV-2 did not develop symptoms.
Other study results suggest that people who are fully or partially vaccinated who have contracted COVID-19 may be less likely to pass the virus to others. For example, vaccinated and infected people had 40% less detectable virus in their nose and therefore lower viral load, and the virus was detected for six days during infection than non-vaccinated people.
In addition, partially or fully vaccinated people were 66% less likely to be infected with the SARS-CoV-2 virus for more than a week compared to non-vaccinated people. Although these indicators are not a direct measure of a person’s ability to spread the virus, they have been associated with a reduction in the spread of other viruses, such as chickenpox and the flu.
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