California will impose a statewide mask mandate for indoor public places regardless of vaccination status for the next month, the state’s top health official announced Monday.

The mask mandate goes into effect Wednesday and will remain in place until Jan. 15, according to Dr. Mark Ghaly, secretary of the California Health and Human Services Agency.

California public health authorities are also recommending that residents who return to the state from travel and tourists who are visiting test for Covid within three to five days of their arrival.

The most populous state in the U.S. is also requiring people attending events with more than 1,000 attendees to submit a negative Covid test if they do not have proof of vaccination. Attendees must submit the test within one day of the event if it is an antigen test and within two days if it is a PCR test.

“We know people are tired and hungry for normalcy. Frankly, I am too,” Ghaly told reporters on a call Monday. “That said, this is a critical time where we have a tool that we know has worked and can work.”

Ghaly said the mask mandate is needed to help reduce Covid infections, which have increased 47% in California since Thanksgiving. The state’s top health official said the heavily mutated omicron strain of the virus has cast uncertainty on the pandemic.

California reported the first confirmed case of omicron in the U.S. on Dec. 1.

New York Gov. Kathy Hochul has also imposed a statewide mask mandate for indoor public places unless the business has a vaccination requirement in place. The New York mandate went into effect Monday and will also last through Jan. 15.

States are taking different approaches to fight Covid as hospitalizations increase across the U.S. Colorado Gov. Jared Polis on Friday said widely available vaccines have made statewide mask mandates unnecessary. He said people are personally responsible for getting vaccinated and the possible health consequences if they do not.

“The emergency is over,” Polis told Colorado Public Radio. “Public health [officials] don’t get to tell people what to wear; that’s just not their job.”

“Everybody had more than enough opportunity to get vaccinated,” Polis said. “At this point, if you haven’t been vaccinated, it’s really your own darn fault.”

About 66,500 Americans are hospitalized with Covid-19, according to a seven-day average of Department of Health and Human Services data through Monday, up 22% over the past two weeks. The delta variant of Covid is driving the increase in hospitalizations, according to the Centers for Disease Control and Prevention.

The omicron variant is now present in more than two dozen states. White House chief medical advisor Dr. Anthony Fauci said earlier this month there’s “no doubt” omicron is spreading through communities in the U.S.

The variant is already rapidly spreading in the United Kingdom, which reported its first death from omicron on Monday. Health Secretary Sajid Javid said omicron now represents 20% of infections in England, and the variant is spreading at a “phenomenal rate.”

It’s unclear whether omicron generally results in more mild or severe symptoms compared with past variants. U.K. Prime Minister Boris Johnson said the rate at which the infection is spreading is worrisome.

“So I think the idea that this is somehow a milder version of the virus, I think that’s something we need to set on one side and just recognize the sheer pace at which it accelerates through the population,” Johnson said Monday.