Masked students walk across the hallway on their first day back at Concord High School in Concord, Calif., on Aug. 12, 2021. (Harika Maddala/Bay City News)

Residents of Alameda County will be allowed to lower not just their Halloween mask on Monday but their COVID-19 one too in certain situations, county health officials announced Thursday.

Residents can lower their masks in some indoor settings when everyone is fully vaccinated, thanks to declining coronavirus cases and hospitalizations in the county.

Eligible settings include controlled spaces closed to the public such as offices, gyms, employee commuter vehicles, and other places, such as churches, where groups gather on a regular basis.

“Allowing vaccinated people to remove their masks in these limited, controlled settings carries lower risk,” Alameda County Health Officer Dr. Nicholas Moss said in a statement. “If vaccinated people choose to continue wearing masks, they should feel comfortable doing so.”

No more than 100 people can gather without masks, everyone must be free of COVID-19 symptoms and the host organization, such as the church or business, must verify that everyone attending is fully vaccinated.

Proof of vaccination can be a vaccination card issued the U.S. Centers for Disease Control and Prevention or a foreign government that includes the person’s name, type of vaccine given, and the date or dates of the dose or doses.

Proof also can be a photo or copy of a vaccination card either on paper or stored on an electronic device, documentation from a health care provider, or a state of California personal digital vaccine record or similar record from another state, local or foreign government.

Hosts must also confirm each person’s identity using a government-issued photo ID.

Mask requirements are still in effect for public settings such as bars, restaurants, and retail stores as well as at K-12 schools. Also, California still requires masks for all unvaccinated people in indoor public places, and everyone must wear a mask in health care facilities, adult and senior care facilities and on public transit.

Employers can check with the California Division of Occupational Safety and Health for requirements for work-related activities.

The city of Berkeley is easing masking requirements too Monday in a similar way as Alameda County. Contra Costa, San Francisco, Marin, and Sonoma counties have eased masking requirements in similar ways recently.

“We’re looking forward to the day when we can safely remove all masking requirements,” Moss said. “To help us get there, we strongly encourage every eligible, unvaccinated person to get vaccinated as soon as possible.

“If you are 65 and older or have increased risk of severe illness due to other health or risk factors or are otherwise eligible, get your booster dose,” he said.