[ExI] Why the CDC says it’s crucial to start wearing masks indoors again

[John Grigg]

"Delta has changed the course of the pandemic in the United States yet
again.

After spurring a summer surge in COVID-19 cases, the more transmissible
coronavirus variant is now driving federal health officials’ decision to
recommend that everyone, regardless of vaccination status, wear masks again
in indoor public places. That’s especially important in areas where
infection rates are high, Rochelle Walensky, director of the U.S. Centers
for Disease Control and Prevention, said during a news conference July 27
to announce revised masking guidelines.

New evidence that vaccinated people with breakthrough infections of the
delta variant produce just as much virus as infected, unvaccinated people
prompted the new guidance. That suggests that these people may also easily
spread the virus. “We have new science related to the delta variant that
requires us to update the guidance regarding what you can do when you’re
fully vaccinated,” Walensky said.

This reverses the CDC’s May recommendation that fully vaccinated people
could ditch the masks. That decision was based, in part, on the low chance
that vaccinated people could spread the virus
<https://www.sciencenews.org/article/cdc-mask-guideline-question-answer-coronavirus-covid-pandemic>
 (*SN: 5/24/21*). If they do get a breakthrough infection, people
vaccinated with one of the mRNA vaccines have about 40 percent less virus
<https://www.nejm.org/doi/full/10.1056/NEJMoa2107058> in their noses than
infected, unvaccinated people do, researchers reported July 22 in the *New
England Journal of Medicine*. But that data was based on infections with
earlier variants of the virus.Unvaccinated people should get vaccinated and
wear masks in public indoor settings until fully vaccinated, she
recommended. Additionally, fully vaccinated people in places with “high or
substantial” transmission rates should also mask up
<https://www.cdc.gov/coronavirus/2019-ncov/vaccines/fully-vaccinated.html> when
indoors again. The CDC considers substantial transmission to be 50 to 100
cases out of every 100,000 people in the population over a seven-day
period. Some places are reporting more than 300 cases per 100,000 people in
a week, she said. “Really an extraordinary amount of viral transmission.”
And everyone in schools should wear a mask, regardless of vaccination
status, the CDC recommends.

“The delta variant behaves uniquely differently from past strains of the
virus that causes COVID-19,” Walensky said. It’s “unlike the alpha variant
we had back in May where we didn’t believe that if you were vaccinated you
could transmit further.” In rare instances, fully vaccinated people may get
infected with the delta variant and spread it to others, new data from
several states and other countries shows, she said. The amount of virus
vaccinated people with a delta variant breakthrough infection produce is
similar to that of unvaccinated people, she said. “This new science is
worrisome,” she said.

The vaccines are still effective at preventing serious illness and death,
studies have shown. Until the vast majority of people are vaccinated, “mask
wearing will help reduce infections, prevent serious illnesses and death,
limit strain on local hospitals and stave off the development of even more
troubling variants, Barbara Alexander, an infectious diseases expert at
Duke University School of Medicine and president of the Infectious Diseases
Society of America, said in a statement.

The majority of transmission is still happening among and through
unvaccinated people, Walensky said. Breakthrough infections remain rare
<https://www.sciencenews.org/article/coronavirus-covid-vaccines-breakthrough-infections-variants>,
but exactly how rare they are with the delta variant isn’t known (*SN:
5/4/21*). The CDC collects data on breakthrough infections in hospitalized
people, but not those who get infected but have mild cases. The public
health agency is also actively testing more than 20 groups of vaccinated
people for COVID-19, including tens of thousands of health care workers,
essential workers and other caregivers. Results of that surveillance will
be reported soon, Walensky said."
https://www.sciencenews.org/article/cdc-covid-coronavirus-masks-indoors-vaccinated-people-pandemic
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