WASHINGTON D.C. (CNN/KDKA) — To prevent further spread of the Delta variant, the U.S. Centers for Disease Control and Prevention updated its mask guidance on Tuesday to recommend that fully vaccinated people wear masks indoors when in areas with “substantial” and “high” transmission of COVID-19, which includes nearly two-thirds of all U.S. counties.

According to the CDC’s COVID-19 data tracker Tuesday evening, Lawrence County is the only county in the Pittsburgh area to have a “substantial” or “high” transmission. Everywhere else in the Pittsburgh area has a “moderate” spread of the virus.

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The CDC cites the Delta variant, saying new science and data about its spread sparked this change.

During an afternoon media briefing, leaders with the CDC told reporters these changed guidelines are extremely important in areas with substantial and high community spread of the virus.

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“Any time public health guidance shifts and there’s misinformation and polarization, it makes it much harder to tell people what they should do or shouldn’t do and who they should trust,” said Dr. Amesh Adalja, senior scholar at the Johns Hopkins Center for Health Security. “Hopefully what we’ll see is more people will see the delta variant threat is real especially in those southern states and start to get vaccinated.”

Adalja is challenging the CDC’s shift, arguing that vaccinations are key.

“We aren’t seeing cases being driven by the fully vaccinated. If you look at where cases are going up, it’s in places where vaccine levels are low. That’s not a coincidence,” he said.

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As for issuing another statewide mask mandate amidst the new guidance, Gov. Tom Wolf said he’s not considering that option. Instead, he’s encouraging people to get vaccinated. In Pittsburgh, a statement says Allegheny County Health Director Dr. Debra Bogen is, as she has been, urging people to follow CDC recommendations.

“The bottom line is everything that’s happening in the United States is in our control. It’s self-inflicted,” said Adalja. “The more vaccines we get into peoples’ arms, the more willing people are to get vaccines, the less likely we are to have any trouble with COVID in the future.”

Dr. Adalja tells KDKA for people living in our area, this shouldn’t be a serious concern.

“It’s really something that is mostly going to apply to those areas of the country that vaccine rollout has been slow, that vaccine uptake has been low, and the vaccine hesitancy level is very very high,” said Adalja.

Meanwhile, the guidance for unvaccinated people remains the same: continue masking until they are fully vaccinated.

Nearly half — 46% — of US counties currently have high transmission and 17% have “substantial” transmission, according to data from the CDC, as of Tuesday morning.

The CDC’s guidelines can be found here.

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Meghan Schiller