Barbara Bent, a library aide at the Central Library in Berkeley, Calif., shelves books in the children's area at the public library in Berkeley, Calif., on Sept. 30, 2021. Bent, who has worked at the library for 20 years, is retiring in October. (Harika Maddala/ Bay City News)

Contra Costa County announced Thursday that it will partially lift its indoor mask requirements Nov. 1 for small, fully vaccinated settings.

The health order will allow fully vaccinated people to remove their masks indoors in settings with fewer than 100 people that are not open to the general public like offices, gyms, occupational vehicles, religious gatherings and college classes.

Those present in such settings must confirm their full vaccination status with the host or business, must gather on a regular basis and should not attend if they have COVID-19 symptoms.

“This will allow vaccinated people to feel safe removing their masks at the office and when they’re working out at the gym,” county Health Officer Dr. Chris Farnitano said. “Of course, people in these places can keep wearing masks if that makes them feel more comfortable.”

Contra Costa County is the third Bay Area county to make partial changes to its indoor mask requirements, joining Marin County and San Francisco. Public health officials in all three counties have pointed to declining COVID-19 cases and hospitalizations as evidence that it is safe to remove masking requirements in some settings.

Indoor mask requirements, regardless of vaccination status, will still be in effect in Contra Costa County in larger indoor spaces like grocery stores, bars and restaurants.

In addition, unvaccinated residents are still required to wear a face covering indoors in any public setting.

On Tuesday, Farnitano said the county could lift its broader mask mandate by New Year’s if the region remains on its current trajectory of declining cases and increasing vaccinations.

Health officials in nine Bay Area jurisdictions, including Contra Costa County, said last week that they would lift indoor mask mandates when each respective jurisdiction reaches a handful of criteria, including 80 percent of a county’s total population being fully vaccinated and reaching the moderate or yellow tier of COVID-19 transmission as defined by the U.S. Centers for Disease Control and Prevention.

As of Thursday, only Marin County has fully vaccinated more than 80 percent of its total population.

In Contra Costa County, 71.6 percent of the county’s total population has been fully vaccinated against COVID-19.

Among those currently eligible for vaccination — those age 12 and older — 82.4 percent are fully vaccinated.