(CNN)More states are relaxing measures to protect against Covid-19 as variants circulate in the United States -- a combination that means "we're walking into the mouth of the monster," an infectious disease expert said.
A variant first identified in the UK has now been reported in 2,672 cases in 46 states as of Thursday, according to the US Centers for Disease Control and Prevention. And it is spreading quickly.
"We literally are sitting on top of that, at a time when instead of actually getting better prepared for it, we're opening up and inviting the virus in," said Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota.
"Right now, that (UK variant) is about to take off the United States," Osterholm told CNN's Jake Tapper. "A number of states have seen it go from 1 or 2% of the viruses identified, to now over 20 to 30%."
This week, Texas and Mississippi joined the list of states to remove mandates for citizens to wear masks and expanded capacity for businesses.
With vaccine eligibility opening up to most US adults by the summer, support for measures to protect against the virus is waning, according to a new survey.
Although less than a third of people said there should be fewer measures, support for additional restrictions has been on the decline since November, according to new research from the Pew Research Center.
But health experts say the road to herd immunity still has a long way ahead, and masks and other restrictions are still crucial to managing the pandemic.
A new CDC study demonstrates "that masks work," CDC Director Dr. Rochelle Walensky said during a White House Covid-19 briefing on Friday.
"You have decreases in cases and deaths when you wear masks and you have increases in cases and deaths when you have in-person restaurant dining, and so we would advocate for policies -- certainly while we're at this plateau of a high number of cases -- that would listen to that public health science," Walensky said.
States range on loosening restrictions
As the US moves closer to widespread vaccinations, many states are changing their policies around Covid-19 restrictions.
In Maine, Gov. Janet Mills said Friday the state will continue to require masks, but she announced a new framework to slowly reopen the state. By March 26, capacity for indoor gatherings in the state will increase to 50% and outdoor will increase to 75%.
And in West Virginia, beginning Saturday, some businesses including restaurants, bars, gyms and museums can open with 100% seating capacity, but social distancing will still be required, Gov. Jim Justice said Friday.
In Texas, any business will be allowed to open 100% beginning March 10, and the order for residents to wear masks has been lifted.
Not all state leaders feel comfortable with the changes.
"I'm deeply concerned about states that lift the mask mandate because what you're doing is sending a signal that it's not important anymore, and that is not true. In fact, it is just as important as ever," North Carolina Gov. Roy Cooper said.
"I would encourage my fellow governors and local officials who are making decisions in some states to keep the mask mandate, to show good examples and to continue doing responsible things."
Detroit mayor declines Johnson & Johnson vaccine allocation
Many experts have celebrated the authorization of the third coronavirus vaccine: Johnson & Johnson's, which is a single shot and is stored at temperatures more convenient for transportation and storage.
But there has been some pushback.
Detroit Mayor Mike Duggan on Thursday said the city declined an initial allocation of the newly authorized vaccine.
Duggan turned down the shipment because the city is able to meet current demand with its supply of the Pfizer/BioNTech and Moderna vaccines -- even as his administration expanded vaccine eligibility Thursday to residents ages 50 and older with chronic medical conditions.
All three vaccines are highly effective at preventing serious illness from Covid-19, and health officials have urged people to take any Covid-19 vaccine they are offered.
"The day may come in March or April when every single Moderna and Pfizer is committed, and we still have people who need a vaccine. And at that point we will set up a Johnson & Johnson center. I don't see that in the next couple of weeks," Duggan said.
CDC guidance for the vaccinated
CDC guidance for people who have been vaccinated is coming soon, Walensky said. The guidance had been expected to release this week.
"Our goal and what is most important is that people who have been vaccinated and those not yet vaccinated are able to understand the steps they can take to protect themselves and their loved ones," she said.
More than 82 million vaccine doses have been given out in the US, and after a year of life turned upside down, many want to know what the future holds.
"I think people need practical advice about how to go about their everyday lives," said Julia Marcus, an infectious disease epidemiologist at Harvard. "I think without guidance, people may make decisions that are not informed."
While the guidelines will not give the vaccinated permission to start living like it's 2019 again, according to a Biden administration official, the guidelines do offer some hope that the end of total social isolation is near.
CNN's Lauren Mascarenhas, Jacqueline Howard, Kay Jones, Anjali Huynh, Amir Vera, Heather Law, Ganesh Setty and Jen Christensen contributed to this report.