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As COVID-19 vaccines continue to roll out in the United States, experts are warning Americans not to let their guards down during what might be one of the "trickiest phases" of the pandemic so far.

A new report in The Washington Post says although COVID-19 cases have come down nationally, cases are "flat or creeping up in much of the Northeast and Mid-Atlantic and parts of the Upper Midwest," and health experts are warning that as states move to re-open, the public must double down on COVID-19 precautions.

"It's like we're in the home stretch where it hurts more than any other time," Florida International University epidemiologist Mary Jo Trepka told the Post. "But if you give up now, you've given up the entire race."

Indeed, the Post writes that "experts recognize this is one of the trickiest phases of the crisis" both "epidemiologically and psychologically," given the public's desire to start returning to normal now that the pandemic appears to be moving toward an end but also as concerning variants spread.

"I keep trying to say, 'Just hold off, hold off, hold off, because the vaccine's coming,'" Harvard T.H. Chan School of Public Health epidemiologist William Hanage told the Post.

CDC Director Rochelle Walensky warned earlier this month that states shouldn't move to roll back COVID-19 restrictions too quickly, as the country could "completely lose the hard-earned ground we have gained." This week, she said cases could potentially climb again if Americans stop following COVID-19 precautions.

"Cases climbed last spring, they climbed again in the summer, they will climb now if we stop taking precautions when we continue to get more and more people vaccinated," she said.