Dr. Anthony Fauci told MSNBC that he'd ask unvaccinated relatives not to attend a family holiday gathering this year due to the omicron surge.

"I think we're dealing with a serious enough situation right now that if there's an unvaccinated person I would say, 'I'm very sorry, but not this time. Maybe another time when this is all over,'" Fauci told MSNBC Tuesday night.

"It's a problem when you're dealing with [a variant] that's spread so rapidly and you are unvaccinated. The virus is going to find you," he said.

Ahead of the holidays, the best way to protect yourself and those around you is still to get vaccinated and boosted, Fauci said. Testing provides another layer of protection, though Fauci acknowledged that if people cannot get ahold of a test, given the increase in demand, they may need to make tough decisions, depending on their individual risk.

-ABC News' Arielle Mitropoulos, Josh Hoyos

California is requiring health care workers to get the booster shot by Feb. 1, Gov. Gavin Newsom announced.

As of Wednesday, California has a 3.3% positivity rate, the lowest in the country, Newsom said. Newsom, however, warned that cases have nearly doubled in one week.

The governor also announced that the state bought 6 million rapid tests to be distributed to school children, so each student has about one or two tests. Students can test at home before returning to classrooms after the holidays, he said.

California is also working on expanding hours at test sites to provide more access, he said.

-ABC News' Nicholas Kerr

For the first time, some New York City subway stations will offer walk-in PCR testing, New York Gov. Kathy Hochul announced Wednesday.

The initiative begins Dec. 27 at the Times Square-42nd St subway station from 8 a.m. to 2 p.m. and at Grand Central Terminal from 3 p.m. to 8 p.m. Testing will be seven days a week but not available on New Year's Day.

Five other subway testing locations will open next week and will be announced when they're finalized, the governor said.

New York also offers vaccinations at some subway stations. Boosters are now available at Times Square-42nd St and Jackson Heights-Roosevelt Av/74 St. Grand Central Terminal will offer boosters beginning Dec. 27, according to the governor's office.

Omicron cases have now been reported in all 50 states, according to an ABC News count.

The South Dakota Department of Health announced Wednesday that officials detected omicron in a young man in his 20s, making South Dakota the final state to confirm the highly transmissible variant.

The CDC on Monday said omicron was estimated to be the dominant variant in the U.S., representing more than 73% of new cases as of Dec. 18.

The CDC warned this week that models, which estimate the trajectory of coronavirus in the U.S., suggest that the number of new omicron infections will likely surge in the weeks to come and could exceed previous peaks.

-ABC News' Arielle Mitropoulos, Darren Reynolds

Six hospitals in Ohio have taken out a full-page ad in the Cleveland Plain-Dealer in a desperate plea for people to get vaccinated as the state faces a renewed surge.

The ad, which appeared in Sunday's paper, says in big letters: "Help."

"We need your help. We now have more COVID-19 patients in our hospitals than ever before," the ad says. "And the overwhelming majority are unvaccinated. This is preventable."

Ohio Gov. Mike DeWine announced last week that he would deploy the state's National Guard to help with hospital strain. Ohio is now averaging more than 9,100 new cases every day -- up 67.5% in the last month. Statewide, more than 5,200 patients are hospitalized with COVID-19.

"The best way to avoid serious illness is the vaccine," the ad said. "So, get vaccinated and get your booster ... we need you to care as much as we do."

-ABC News' Arielle Mitropoulos