MARIN COUNTY (CBS SF) – More than 110 new COVID-19 cases were reported in Marin County on Tuesday, which health officials are attributing to the rapidly spreading omicron variant.

According to health officials, 112 new cases were reported Tuesday alone, the highest total since January 13. During the surge in cases driven by the delta variant over the summer, the highest daily count was 86 new cases.

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The spike in cases comes less than a week after Marin County confirmed its first cases of the highly contagious variant.

“We’re deep into the transition to Omicron,” Marin health officer Dr. Matt Willis said Wednesday. “Given the detection in Marin wastewater last week, increased number of confirmed cases regionally, yesterday’s spike in cases, and the emerging national data, we should assume new cases are most likely due to Omicron.”

Earlier this week, Willis said he expected omicron to be the dominant variant as kids were returning to school from the holidays. The county had distributed more than 96,000 kits to students to self-test before coming back from vacation.

Officials said that cases so far have not led to major spikes of serious illnesses in the heavily vaccinated county, which has nearly 92% of eligible residents fully vaccinated.

As cases rise, health officials urge residents more than six months from their last shots to receive their boosters, saying that two doses are not enough to effectively protect against omicron infection.

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“The unfortunate reality is we’re seeing more cases in fully vaccinated people. You really need to booster to be well protected. Fortunately, infections among vaccinated people are generally mild.” Willis said.

According to the county’s vaccination dashboard, about 105,500 out of the county’s 245,000 residents eligible for vaccination have received a booster.

Officials also urge people to wear masks indoors. Testing is recommended when symptoms arise, along with before and after travel and holiday gatherings.

People hosting holiday gatherings are being urged to keep capacity small, to ideally meet outdoors or in well-ventilated indoor spaces, to keep a list of attendees in the event of a positive test and to urge attendees to take rapid tests on the day of the gathering.

For people at risk of more serious illness and who have not received their booster shots, officials urge people to skip gatherings or to participate remotely. People who are sick should also avoid gatherings.

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Officials said there are “no immediate plans” to enact new COVID-19 restrictions, citing the availability of vaccines and booster shots that were not available to the general public last winter.