An internal Centers for Disease Control and Prevention document obtained by several news outlets warns that the COVID-19 delta variant could be more likely to produce severe illness and can spread as fast as chickenpox.

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The Washington Post, which was first to report on the CDC slide presentation, said new research also indicates that fully vaccinated people can spread the virus at higher rates than previously thought. The paper reported that the CDC document says health officials need to acknowledge the "war has changed."

The CDC did not immediately respond to an after-hours email from Fox News. The information in the document reportedly played a role in the new mask guidelines announced earlier this week. The Biden administration has been more assertive in recent days to compel Americans to sign up for a vaccine due to the emergence of variants.

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Admiral Brett Giroir, the former assistant health secretary under President Trump, told Fox News’ "America Reports" on Thursday that the variant is so contagious that it is "just a matter of time" before everyone who is not vaccinated and hasn’t had COVID-19 comes down with the infection.

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"If you have prior immunity you do have some protection, but more and more data are telling us that that protection is not so good against delta," he said. "Remember, you can get the flu every year. It’s not because your immunity isn’t good. It’s because the flu changes and delta is really a new strain that is different than everything we’ve seen. So, I am really concerned that natural immunity, although real, is not going to be sufficient against Delta."

Giroir’s comments seem to echo the CDC’s document. The agency said there needs to be a new public messaging to get people to sign up for the vaccine.

There have been lingering issues for those resistant to the vaccines. The Food and Drug Administration has not fully approved the jabs that are still being administered under an Emergency Use Authorization.

The death count in the U.S. also remains comparatively low. There were 398 deaths due to the virus on Thursday in the U.S. compared to the winter months when the numbers were 10 times that amount.

Matthew Seeger, a communication expert at Wayne State University, told the Post that health officials may have had some messaging issues with the public.

"We’ve done a great job of telling the public these are miracle vaccines," he said. "We have probably fallen a little into the trap of over-reassurance, which is one of the challenges of any crisis communication circumstance."

The Post’s report pointed out that fully vaccinated people who come down with the delta variant can carry the same viral load as those without the vaccine and infect others.

The New York Times, which also viewed the document, reported that Dr. Rochelle P. Walensky, the head of the CDC, has said transmission from vaccinated individuals is rare, but some scientists believe it is more common than earlier believed.

John Moore, a virologist at Weill Cornell Medicine, told the Times that Delta "is the troubling variant we already knew it was."

"But the sky isn’t falling and vaccination still protects strongly against the worse outcomes," he said.

Get updates on this story at FOXNews.com.

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