People who have been vaccinated against coronavirus are more than 90% protected against infection and, if they do become infected, they have milder disease than unvaccinated people, a new Centers for Disease Control and Prevention study shows.
The ongoing, real-life study also shows even partially vaccinated people are 81% less likely to become infected than unvaccinated people, the CDC team reported.
The study of more than 3,900 health care staff, first responders and other frontline essential workers who have been tested weekly since December showed that so far 5% have tested positive for coronavirus. Only 16 of the 204 people who became infected had been vaccinated.
The findings are reported in an online preprint on the medrxiv site and have not been peer-reviewed or published in a medical journal.
“This adds to the growing body of real-world evidence of their effectiveness,” the CDC said in a statement.
“Findings from the extended timeframe of this study add to accumulating evidence that mRNA COVID-19 vaccines are effective and should prevent most infections — but that fully vaccinated people who still get COVID-19 are likely to have milder, shorter illness and appear to be less likely to spread the virus to others. These benefits are another important reason to get vaccinated," CDC Director Dr. Rochelle Walensky added in the statement.
The workers got either Pfizer/BioNTech’s or Moderna’s two-dose coronavirus vaccine and have been testing themselves weekly since December, regardless of whether they have symptoms. That’s the only way to tell if the vaccines prevent asymptomatic infections.
Those who got “breakthrough” infections after one or two doses of vaccine had 40% less virus in their bodies and were 58% less likely to have fever. They spent two fewer days in bed than unvaccinated Covid-19 patients.