"People need to be careful," said UCSF's Dr. George Rutherford. "Attend smaller events and try to attend events where everyone has been vaccinated and boosted."
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Rutherford advises anyone attending large indoor gatherings to wear masks. He says the "threshold" for indoor gatherings follows common sense - a handful of couples, not hundreds of people.
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Yet, plenty of those events are still happening across the Bay Area Friday night, according to Eventbrite.
In San Francisco, at least 400 people are scheduled to attend an annual New Year's Eve yacht party set to sail off at Pier 3, according to the event organizers.
It costs $350 per ticket for four hours of dancing and an open bar.
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Even though proof of vaccination is required, large gatherings like these are considered "high risk" - even for people who've received their booster shots.
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It comes as the CDC just released updated guidance, warning against cruise travel regardless of vaccination status, citing how quickly the virus can spread in close quarters.
"We know of lots of events, including a big party in Marin County a couple weeks ago where there was a lot of transmission... even though everyone was vaccinated and boosted," said Rutherford.
The next two weeks are expected to be the most infectious period of our current Omicron surge as the variant already accounts for roughly 50 to 70 percent of new COVID cases across the state.
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"We take one step forward and two steps back," said Mike Donahue, a member of the Corinthian Yacht Club in Marin.
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He's relieved the club canceled its annual New Year's Eve ball due to COVID concerns.
"There's just a lot of fear of omicron and it's not worth the risk."