New CDC mask guidance was based on study of outbreak at Cape Cod beach party

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The Centers for Disease Control and Prevention released a study Friday backing up its stricter new mask guidance, one that concluded that people infected with delta variant may transmit COVID-19 even if they’re vaccinated, based on an outbreak at a Cape Cod beach party.

The study found that vaccinated subjects had nearly the same amount of virus in their bodies as the unvaccinated, suggesting they were as likely to transmit the virus to others.

Still, the authors included major caveats in the study, most notably that it only included subjects who happened to get tested, a limitation that could bias the results. The outbreak also took place in a setting that is not representative of the country as a whole — the beach town Provincetown, Massachusetts, a popular gay destination, during a major summer party event. Thousands of attendees gathered in densely packed crowds both indoors and outdoors, making person-to-person transmission more likely.

VACCINATED PEOPLE INFECTED WITH DELTA VARIANT MIGHT BE CONTAGIOUS, CDC SAYS IN JUSTIFYING MASK GUIDANCE

“High viral loads suggest an increased risk of transmission and raised concern that, unlike with other variants, vaccinated people infected with delta can transmit the virus,” CDC Director Rochelle Walensky said Friday. “The masking recommendation was updated to ensure the vaccinated public would not unknowingly transmit virus to others, including their unvaccinated or immunocompromised loved ones.”

Public health experts concluded that, of the 469 COVID-19 cases that were identified, the vast majority involved the delta variant, and nearly 75% occurred in fully vaccinated people.

While it was only published Friday, the study was one of several the CDC cited earlier this week in rolling out new recommendations that people in most of the country wear masks indoors. The agency also cited a study performed by Indian researchers as well as a study of breakthrough cases in Houston, Texas.

The study published Friday also reported that four of the five people who had to be hospitalized were fully vaccinated.

“Findings from this investigation suggest that even jurisdictions without substantial or high COVID-19 transmission might consider expanding prevention strategies, including masking in indoor public settings regardless of vaccination status, given the potential risk of infection during attendance at large public gatherings that include travelers from many areas with differing levels of transmission,” the report said.

Public health experts maintain the vaccines are very effective at preventing serious illness and death due to the coronavirus.

“The vaccines are largely working as expected. We had an outbreak in P-town with lots of vaccinated folks infected. No one died. Very few got sick. And things have returned to normal. This is how vaccines work folks,” said Dr. Ashish Jha, a prominent Brown University public health expert.


Provincetown city manager Alex Morse also insisted on Friday the situation was under control, noting the test positivity rate peaked at 15% on July 15 but fell to 4.8% on Thursday.

“The vaccines are working. Of the 900 cases related to the Provincetown cluster, there have been no deaths, seven hospitalizations, and the symptoms are largely mild,” Morse said on Friday. “The outbreak is contained and Provincetown is safe.”

WHITE HOUSE DEFENDS MOVES TO MANDATE COVID-19 VACCINE

The Biden administration changed tack recently in its bid to boost vaccination rates that have lagged in the past couple of months. President Joe Biden announced that federal workers would be required to provide proof of vaccination or submit themselves to regular COVID-19 testing.

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