'Breakthrough' cases, high COVID-19 viral load cited in study that led to new CDC mask guidance

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Posted at 12:23 PM, Jul 30, 2021

WASHINGTON, D.C.- The Centers for Disease Control (CDC) released new data Friday which it says guided its decision to update its mask recommendation.

The July study cites 469 cases of COVID-19 in Barnstable County, Massachusetts. It says 74% of cases occurred in people who are fully vaccinated, most of which were symptomatic. The Delta variant was the main cause of infection, the study says.

The study said four fully vaccinated individuals were hospitalized, and no deaths were reported.

The data suggests that those who are fully vaccinated had similar viral loads to those whose vaccination status was unknown.

"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," said Dr. Rochelle Walensky, director of the US Centers for Disease Control and Prevention, in a statement Friday.

The CDC believes people wearing a mask can prevent further spread of the Delta variant, which has transmissibility that’s been compared to chickenpox.

Fears of the Delta variant appear to be leading to a surge in vaccinations.

Cyrus Shahpar, the COVID-19 data director for the White House, said Thursday marked the highest number of people vaccinated against the virus since July 1.

He tweeted that 69.6% of Americans have received at least one dose of the vaccine.