CDC: New data suggests vaccinated people could transmit delta variant

Director of the U.S. Centers for Disease Control and Prevention Dr. Rochelle Walensky expressed concern over new data that shows that vaccinated and unvaccinated people infected by the delta variant of the novel coronavirus carry viral loads that "are actually quite similar."

"We are actively conducting outbreak investigations of what’s occurring in places that are having clusters... What we’ve learned in that context, is when we examine the rare breakthrough infections and we look at the amount of virus in those people, it’s pretty similar to the amount of virus in unvaccinated people," Walensky said. 

The news comes as the CDC announced new recommendations on Tuesday that vaccinated people return to wearing masks indoors in parts of the U.S. where the coronavirus is surging.

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The new data suggests that vaccinated people "may be contagious and spread the virus to others," Walensky said.

But Walensky noted that vaccinated people are still unlikely to become severely ill from COVID-19. 

Walensky also said that most of the cases and hospitalizations related to COVID-19 are coming from people who are not yet vaccinated. She pleaded with Americans to get inoculated in hopes of not overwhelming the nation’s hospitals.

"Of the transmission that’s happening in country right now, a vast majority of transmission is occurring through unvaccinated people. But on the exception that might have a vaccination breakthrough, (the CDC) thought it was important for people to know they could pass the disease onto someone else," Walensky said.

Walensky said the CDC is currently monitoring breakthrough cases of the virus, and said the biggest concern is from areas where people are not getting their shots. 

RELATED: Delta variant viral load 1,000 times higher than original coronavirus strain

"But, again, I want to reiterate — the vast majority of transmission is occurring in unvaccinated people and through unvaccinated people. But unlike the alpha variant that we had back in May, where we didn’t believe that if you were vaccinated you could transmit further — this is different now with the delta variant. And we’re seeing that now, infection is possible if you are a rare breakthrough infection, that you can transmit further which is the reason for the change," Walensky added. 

Walensky’s remarks came in the wake of a study published on July 7 and led by Chinese epidemiologist Jing Lu at the Guangdong Provincial Center for Disease Control and Prevention in Guangzhou, China found that the delta variant contains 1,000 times more viral material than that of the original novel coronavirus variant that infected much of the global population during the onset of the global pandemic last year.

Study authors noted that this characteristic is what makes the variant so worrisome and contagious. The delta variant can replicate at a much faster rate than the original strain, making the mutation much more infectious, according to the study.

When a person becomes infected with the delta variant, the mutation is shedding significantly more viral material, making it harder to suppress and easier to infect others.

Researchers also found that on average it took approximately four days for the delta variant to reach detectable levels using a standard COVID-19 test kit compared with the six days it took for the original coronavirus strain to be detected.

Experts believe the delta variant spreads more easily because of mutations that make it better at latching onto cells in human bodies. On its website, the U.S. Centers for Disease Control and Prevention notes "increased transmissibility" with the delta variant and the potential for it to make certain monoclonal antibody treatments less effective.