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Why masks are still needed even after getting vaccinated

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In a report published today (Monday) in the MMWR, scientists at the U.S. Centers for Disease Control (CDC) report more good news from real-world studies of people who have been vaccinated against COVID-19.

In the study involving 3,950 health care workers, first responders and other essential workers who were vaccinated between December 2020 and March 2021, the researchers found that the two-dose vaccines are 90% effective in protecting people from getting infected with SARS-CoV-2, the virus behind COVID-19. A single dose of the shot provided 80% protection from infection.

The people in the study were vaccinated with one of the first two authorized shots, from Pfizer-BioNTech and Moderna, which both require two doses and rely on mRNA technology. In the studies that both companies provided to the U.S. Food and Drug Administration to earn emergency use authorization, the shots were 94% to 95% efficacious in protecting people from getting sick with COVID-19.

What the studies didn’t show was whether vaccinated people were also protected from getting infected with the virus in the first place. These new, real-world findings show that the vaccines also protect against infection itself, a critical extra layer of protection, since anyone who is infected can spread the disease to others, even if they don’t experience any symptoms themselves.

The fact that the mRNA vaccines are 90% effective in protecting people from infection is an important benefit of the shots.

But, say experts, the encouraging news doesn’t mean that vaccinated people can shed their masks. And that’s because of new variants of the virus that have emerged that the vaccines were not designed to target. The study didn’t show whether vaccinated people are also protected from infection with one of the variants now circulating around the world.

That means that people vaccinated with either the Pfizer-BioNTech or Moderna shots can still get infected, and sick, if they are infected with one of these variants, albeit not as severely sick as they might have if they hadn’t gotten the shots. In addition, they could also still pass along the variant virus to others.

“People may interpret these results as meaning, ‘Great, now that I’m vaccinated I don’t need to wear a mask because I’m not at risk of infection,’” says Dr. Paul Offit, director of the vaccine education center at the Children’s Hospital of Philadelphia and member of the FDA advisory committee that reviews vaccines. “The problem with that are the variants. You can still get sick if you are exposed to a variant, and you can still shed and spread the virus.”

Plus, while vaccinated people are much less likely to get infected, and therefore much less likely to spread the virus, it’s still not entirely clear that they are not contagious, if they do happen to get infected. “Until there is a lot less transmission in the community, I will continue wearing a mask,” says Dr. Carlos Del Rio professor of medicine at Emory University, who has been vaccinated. “The protection against infection wasn’t perfect—80% to 90%. Can I increase that to closer to 100% by wearing a mask? Yes.”  ...

 

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