In Washington, D.C., a vaccine mandate for restaurants, nightclubs, bars and indoor venues is set to begin on Jan. 15.

But 19 House Republicans sent a letter to Mayor Muriel Bowser on Monday saying that the mandate "will not prevent the virus from spreading." 

"This sweeping mandate, however, will harm the District’s economic recovery and lock many Americans out of their capital city," the Republicans wrote, adding, "We urge you to withdraw the Order."

The city is seeing some improvement in COVID-19 case numbers, D.C. Health’s senior deputy director, Patrick Ashley, told reporters on Monday.

"We're very hopeful based on that data that we are getting to a better spot," Ashley said. "It's still certainly high. It's still an area for concern and we don't expect that to go down overnight.”

-ABC News' Beatrice Peterson

In New Jersey, hospitalizations are at the highest point since April 2020, and the number of patients in ICUs and needing ventilators are on the rise, Gov. Phil Murphy said Monday.

"We’re in the thick of this latest fight against the omicron tsunami marching across the state," the governor said at a news conference.

New Jersey is recording more deaths now than at any point in the last year and more daily cases than any point of the pandemic, he said.

Murphy added on Twitter, "The percentage of infections among individuals who have at least completed their primary vaccination courses has been creeping up over the past several weeks – but the unvaccinated are still the ones testing positive by a rate of more than two-to-one."

-ABC News' Matthew Foster

U.S. hospitalizations have reached a record high with more than 141,000 Americans now in hospitals with COVID-19, according to data from the Department of Health and Human Services.

It's not clear how many of these patients were admitted to the hospital for COVID-19 and how many people tested positive for the virus after they were admitted for other reasons. 

About 25.3% of U.S. hospitals with available data are reporting critical staffing shortages.

In the last week, the U.S. has reported nearly 4.7 million new COVID-19 cases -- the highest weekly case number on record, according to federal data.

Roughly one in every 70 Americans tested positive for COVID-19 this week alone.

New York City holds the nation's highest case rate.

-ABC News' Arielle Mitropoulos

Some immune-compromised Americans will be eligible for a fourth dose this week. 

A third dose for people with compromised immune systems was recommended by the CDC on Aug. 13. The CDC recently shortened the window of Pfizer and Moderna booster shots from six months to five months. This means immune-compromised people who got a third shot in mid-August will be eligible for a fourth dose in mid-January.

People with immune compromised conditions make up about 3% of the U.S. population.

-ABC News' Sony Salzman, Arielle Mitropoulous