Centers for Disease Control and Prevention Director Dr. Rochelle Walensky insists that new coronavirus guidance on mask-wearing is solely based on science and not the result of political pressure. 

The CDC issued new guidance last week that says people who are fully vaccinated can stop wearing masks, both indoors and outdoors. The announcement came just one day after Walensky spoke in Congress and defended the stance that masks were necessary. 

Walensky told "Fox News Sunday" host Chris Wallace that the CDC has always followed "evolving data" on the pandemic.

"It certainly would have been easier if this science had evolved a week earlier and I didn’t have to go to Congress making this statement," Walensky said. "But I'm delivering the science … and you know, it evolved over this last week." 

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Walensky pointed to two studies that published last Thursday – the same day the CDC changed its guidance. Both papers were published in the New England Journal of Medicine.

Centers for Disease Control and Prevention Director Dr. Rochelle Walensky testifies during a Senate Health, Education, Labor and Pensions Committee hearing to examine an update from Federal officials on efforts to combat COVID-19 on Tuesday, May 11, 2021, on Capitol Hill, in Washington. (Greg Nash/Pool via AP) (Greg Nash/Pool via AP)

The CDC's announcement was met with immediate action, with at least 17 states now relaxing or dropping mask requirements, with more expected in the next few weeks. Most of those states have left the power to regulate mask usage in the hands of local leaders and businesses, though some are questioning how businesses can ensure safety if they cannot verify vaccine status.

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Walensky maintained that such fears are unfounded, citing the rate of vaccinations nationwide as reassurance that people will remain safe. 

"We are still vaccinating somewhere between 1.5 and 2 million people a day," Walensky said. "So every day more and more people are getting vaccinated. The honor system is to be honest with yourself. If you are vaccinated, we are saying you are safe, you can take off your mask and you are not at risk of severe disease or hospitalization from COVID-19."

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"If you are not vaccinated, you are not safe," she added. "Please, go get vaccinated or continue to wear your mask."