Personal trainers interact with their clients at Red Dot Fitness Gym, in San Jose, Calif., on June 15, 2021. While June 15 marked the first day for the gym members to workout with out a mask, gym trainers continue to wear a mask until further notice from the county. (Harika Maddala/Bay City News)

Three more Bay Area counties issued recommendations this week that their residents should resume wearing a mask indoors, regardless of vaccination status, as COVID-19 cases tick up across the state.

Napa, Santa Cruz and Monterey counties jointly issued an advisory Monday with San Benito County to recommend that residents in all four counties wear face coverings when inside public places like grocery and retail stores, theaters and family entertainment centers.

Health officials in the four counties argued that while they didn’t plan to reimplement a full mask mandate, the recent statewide uptick in new cases – primarily among unvaccinated people – and the ascendance of the more contagious delta variant group are both concerning trends.

“Fully vaccinated people are well-protected from infections and serious illness due to COVID- 19 including the Delta variants,” the four counties said in a joint statement. “Vaccinating as many people as possible, as soon as possible, continues to be our best defense against severe COVID-19 infection and the harm it can do to our region.”

The advisory came three days after health officials in Alameda, Contra Costa, Marin, San Francisco, San Mateo, Santa Clara and Sonoma counties and the city of Berkeley issued the same guidance “out of an abundance of caution.”

Local, state and federal public health officials have warned that the pandemic is now progressing on twin tracks, with unvaccinated people increasingly in far more danger of serious illness and death due to COVID-19 than their fully vaccinated counterparts.

While unvaccinated residents have been required by the state to wear face coverings in indoor spaces even after the state’s June 15 reopening, which also included lifting the mandate for fully vaccinated people, the enforcement mechanism for ensuring unvaccinated people keep their masks on has largely been limited to self-attestation.

Health officials in the four counties urged local businesses to go one step further by adopting universal mask requirements when their customers are indoors.

“This will also make it easier for businesses to be sure unvaccinated people are masked,” the four counties said.

Roughly 56 percent of eligible Santa Cruz County residents are fully vaccinated, while 73 percent of eligible Napa County residents are fully vaccinated and 70 percent of Monterey County residents have received at least one vaccine dose.

Unvaccinated or partially vaccinated residents are encouraged to visit to find a vaccination site near them, many of which now accept walk-in appointments.

Health officers across the Bay Area said they plan to revisit the mask recommendations in the coming weeks to determine if further action is needed, including implementing a fresh mask mandate.