Maine reported its first cases of the more contagious omicron variant on Friday in five samples from Penobscot County following a genomic sequencing of positive test results recently reported to the Maine Center for Disease Control and Prevention.

The detection of the fast-spreading coronavirus variant came on the same day state health officials reported 1,150 new cases of COVID-19, 25 deaths and a record 383 people hospitalized.

Omicron may cause less severe illness than the delta variant that has fueled the fall surge, but officials say it may add to the burden hospitals are facing because it spreads more easily.

Omicron has quickly ramped up infections in countries like South Africa, the United Kingdom, Denmark and Norway. And COVID-19 is soaring  in New York City, suspected to be fueled by exponential growth in the omicron variant. The variant has been detected in 41 states, including Maine, according to the Maine CDC. The U.S. CDC currently estimates 3 percent of all cases nationwide are the omicron variant, but those numbers are expected to grow quickly because the variant is so contagious.

The arrival of omicron in Maine is unwelcome but not unexpected, Gov. Janet Mills said. “We knew it was only a matter of time before we detected the presence of omicron here in Maine,” Mills said in a news release. “While we are still learning about this new variant, the takeaway for Maine people should be this: get vaccinated now and wear a mask when you’re indoors in public.

“Whether it’s your first shot or your third shot, getting vaccinated can protect your health, keep you from getting seriously sick and even save your life.”

Dr. Ashish Jha, an infectious-disease expert with the Brown University School of Public Health, said in a series of tweets on Friday to expect another surge in cases, a “disruptive” January, and to avoid holiday parties and other large gatherings.

“We should expect a large wave of infections, likely gathering steam in late December, peaking sometime in mid-January,” Jha said in a tweet. “And likely falling quickly to low numbers by end of February.”

Jha also tweeted that getting the booster shot is key.

“We’ll see lots of infections. Boosted folks will largely do fine. Others will get infected at high rates,” Jha said. “Unvaccinated and high-risk folks with breakthroughs will be at risk for hospitalizations.”

Preliminary studies are showing that vaccines become less effective against omicron over time and that re-infection is more possible for people who had previously been infected and remain unvaccinated. People who had previously fallen ill from COVID-19 but remain unvaccinated have a five-fold greater chance of being reinfected with omicron compared to previous variants, according to a study released in the U.K. on Friday.

Studies also indicate that booster shots provide similar protection against omicron compared to a fully vaccinated – but non-boosted – person against delta and previous variants.

“Boosters were important before. They are more important now,” Dr. Nirav Shah, director of the Maine CDC, said during a media briefing on Thursday. Maine is now administering about 10,000 shots per day – levels not seen since the spring – with about seven out of every 10 shots being boosters. Maine has given about 400,000 booster shots, representing about 30 percent of the state’s 1.3 million residents.

The U.K. study shows a range of 55 to 80 percent protection against infection for those vaccinated and boosted.

Shah said in a tweet on Friday that the science is still in the early stages on omicron.

“Judging by some publications, omicron is Schrodinger’s variant: it is simultaneously bad and not bad. Of course, it’s too early to know with certainty,” Shah said.

Since the pandemic began, Maine has recorded 135,320 cases of COVID-19, and 1,430 deaths. Maine had 383 people hospitalized for COVID-19 on Friday, a record, with 113 in intensive care and 69 on ventilators.

Of Friday’s 25 reported deaths, 19 were from a periodic review of death certificates, with those deaths occurring between Nov. 11 and Dec. 1.

There continues to be a wide disparity among counties, with high-vaccination counties such as Cumberland recording fewer cases per capita when compared to low-vaccination counties. Aroostook County had the highest seven-day total of 689 cases per 100,000 population. Cumberland County, the most-vaccinated county in Maine, had the second-lowest virus prevalence at 349 cases over a seven-day period per 100,000 population.

Knox County has the second-highest vaccination rate in Maine – at 76 percent fully vaccinated, compared to 81 percent for Cumberland County – and the lowest per capita infection rate over the past week, with 259 cases in seven days per 100,000 population.

The disparity also is present among those who have received booster shots, although the gap is not as wide. Lincoln County led the counties with 37 percent of its population boosted, compared to a low of 22 percent in Somerset County. The statewide average was 30 percent.

Pop-up walk-in clinics continue to be announced in a race to get people their booster shots before the omicron wave intensifies.

The former Pier 1 at the Maine Mall is hosting a walk-in vaccination clinic operated by Northern Light Health. The hours are 9 a.m. to 6 p.m. on Friday and noon to 5 p.m. on Saturday, as well as 1-7 p.m. on Dec. 21-23. Northern Light also is hosting an appointment clinic at Northern Light Health Center, 885 Union St. in Bangor. To make an appointment, go to covid.northernlighthealth.org or call 207-204-8551.

The Westbrook Fire and Rescue Department is holding a one-day, walk-up clinic from noon to 8 p.m. on Dec. 21 at the Westbrook Community Center at 426 Bridge St.

Also, MaineHealth is hosting a vaccination clinic at 110 Free St. in Portland from 8:30 a.m. to 5 p.m. on Monday and Tuesday. On Monday, the clinic is walk-in, while on Tuesday it’s by appointment. To schedule an appointment, go to vaccine.mainehealth.org.

Staff Writer Rachel Ohm contributed to this report.