The pandemic mask picture will look noticeably different in parts of the Bay Area as of Monday.
The biggest change is in Marin County: Starting Monday, officials there will lift all indoor mask restrictions for people fully vaccinated against COVID-19. It’s the first such move in the region after Marin met a set of coronavirus transmission and vaccination benchmarks agreed to by most Bay Area counties.
Meanwhile, Alameda and Contra Costa counties will join San Francisco and Sonoma counties Monday when they ease their mask mandates for fully vaccinated people in some indoor settings.
Here’s what you need to know about mask rules for all Bay Area counties:
Marin County: Mask rules lifted for fully vaccinated people
Starting at noon Monday, fully vaccinated people can go without face coverings in most public indoor settings in Marin County. That includes restaurants, retailers, grocery stores, bars and churches.
Previously, people who had been immunized with either two shots of Pfizer or Moderna or one shot of Johnson & Johnson could take their masks off only in select indoor spaces where everyone present was vaccinated and the same people came in day in and day out.
But Marin County has now met the criteria set by eight of nine Bay Area counties in September allowing counties to ease their restrictions: Namely, it has been in the Centers for Disease Control and Prevention’s yellow “moderate” transmission tier for more than three weeks, has reported low hospitalization rates and has fully vaccinated at least 80% of the population.
Under the new guidelines, individual businesses can still require masks. Under a state order, K-12 schools will still require masks, and face coverings are still required on public transportation and in nearly all health care facilities.
People who are unvaccinated or partially vaccinated (just one dose of Pfizer or Moderna) still must wear masks indoors.
Alameda, Contra Costa, San Francisco, Sonoma: Some restrictions eased
Starting Monday, Alameda and Contra Costa counties will join San Francisco and Sonoma counties in easing some mask restrictions.
Specifically, people who have been fully vaccinated will now be allowed to go without masks in certain indoor spaces where everyone is immunized. That includes offices, gyms, college classrooms and similar environments.
No more than 100 people may be inside, and the same group of people must regularly come to the space.
Operators of such indoor settings can still choose to impose their own face covering restrictions, according to health officials. And in all other public indoor settings, masks are still required for everyone, regardless of vaccination status.
Napa, San Mateo, Santa Clara: Masks still required indoors for all
Masking rules instituted in August in response to the delta variant are still in place in San Mateo, Santa Clara and Napa counties.
All indoor public spaces still require masks for everyone, regardless of vaccination status.
Solano: Masks encouraged but not required
Solano County was the only Bay Area county that did not issue universal indoor masking rules. Masks are still recommended, but only unvaccinated people are required to wear them indoors in that county — except in the cities of Vallejo and Benicia, which issued rules in alignment with the rest of the Bay Area.
How long will it take for the Bay Area to remove all face mask requirements?
The changes in mask mandates are dependent on several criteria, but the hardest to reach has been the requirement that 80 percent of people in the county must be fully vaccinated.
In lieu of hitting the 80 percent goal, counties can wait until COVID vaccine has been available to children ages 5 to 11 for at least eight weeks. Most won’t qualify under that criteria until late December or early January, experts said.
Gwendolyn Wu is a San Francisco Chronicle staff writer. Email: gwendolyn.wu@sfchronicle.com