New Jersey Gov. Phil Murphy on Monday joined the growing chorus of pandemic leaders who are recommending everyone, regardless of vaccination status, take extra precautions this Christmas week.

As the state’s daily new case count reached levels not seen since January, the governor urged residents to take a rapid test before holiday gatherings and to get their booster shots if they are eligible and have yet to do so.

“The last thing anyone wants is for a holiday gathering to lead to more cases,” Murphy said. “Even if you aren’t showing any symptoms, we encourage you to go get tested before visiting with people outside of your household to give yourself that added level of knowledge that you are in the clear.”

“Let’s spread cheer,” added state Health Commissioner Judith Persichilli, “not COVID.”

New Jersey officials stopped short of advising against indoor gatherings, as Philadelphia Health Commissioner Cheryl Bettigole did last week.

» READ MORE: Don’t have indoor Christmas parties, Philly’s top health official says amid COVID-19 surge

Murphy’s warnings came amid increasing fears about the omicron variant, which is extremely transmissible and appears better able to evade vaccine protection than earlier mutations. Omicron has already caused an intense surge of infections in New York, where confirmed cases more than doubled last week.

Public health officials have warned the variant could make for a challenging winter, especially for unvaccinated people, who are more likely to be infected and far more likely to be hospitalized or die from the virus.

Cases are rising in New Jersey, too, due to what Perschilli says is likely a mix of omicron and the still-dominant delta variant. Average daily cases have jumped 66% in the state over the past two weeks, reaching levels not seen since January. While hospitalizations have also increased, they remain overall ”just a fraction of what they were at this time last year,” Murphy said.

The same cannot be said for Pennsylvania, where hospitals in the central and western parts of the state have already reached capacity as they deal with the COVID-19 surge and pandemic-related staffing shortages. Hospitals in the Philadelphia region have so far been faring better. Pennsylvania’s average daily new cases remain at a high level — about 7,500 a day — but have not increased in the past two weeks.

» READ MORE: Full ICUs, 100 dying a day: The winter coronavirus surge is straining Pa.’s health-care system

The Pennsylvania Department of Health advises residents to follow CDC holiday guidance — which advises people to get vaccinated, avoid indoor crowds, and “consider” self-testing before gathering inside with people from other households — a spokesperson said last week. The spokesperson said they “anticipate” acting Secretary of Health Keara Klinepeter, who has not held a news conference since being named to the role last week, will address residents before Christmas.

Philadelphia, meanwhile, has had an average of 641 new cases of COVID-19 per day in the past two weeks, a period during which 7.2% of coronavirus tests were positive. Just before Thanksgiving, the city had an average of 254 new cases per day and a positivity rate of 2.6%.

City officials blame the cold weather and indoor gatherings for the case surge it has seen since then, and hospitals are bearing the brunt. As of Monday, there were 387 coronavirus patients in Philadelphia hospitals, with 44 of them on ventilators. That number has also grown; there were 195 patients hospitalized on Nov. 22.

Some officials have said that an increase in booster shots, along with other mitigation measures, could help blunt the surge.

Moderna said Monday that an additional dose of its vaccine “should provide some good level of protection [against omicron] as we go into the holiday season,” echoing previous findings by Pfizer about the protection of its boosters.

Only about 31% of eligible Pennsylvanians, excluding Philadelphia residents, and 40% of eligible New Jerseyans have gotten their booster shots, a number Murphy said he would like to see increase.

» READ MORE: How many Philadelphians need boosters? Vaccine-tracking challenges make it ‘impossible to say.’

“Quite frankly, with what we know now about the omicron variant, if it is time for your booster, get it now,” the governor said. “Plain and simple.”

Low booster uptake is especially concerning at New Jersey’s long-term care facilities, where less than 38% of eligible employees have received the additional shots, Persichilli said. About 78% of eligible residents have done so.

”Both of these numbers are too low,” she said. “The staff number is especially concerning,” particularly as an increasing number of people are being infected. As of Monday, coronavirus cases had been identified at 205 of New Jersey’s long-term care homes, Persichilli said.

Staff writer Laura McCrystal contributed to this article.