Mask freedom for the vaccinated has proven short-lived in Los Angeles, where county health officials are urging everyone to keep wearing face coverings in grocery and retail stores, theaters and other indoor places in which state and national guidance now says the immunized don’t need them.

And while state and Bay Area health officials aren’t signaling a similar walk-back of the mask rule they loosened just two weeks ago, several infectious disease experts said with the troubling COVID-19 Delta variant on the rise, a recommendation such as L.A. County’s wouldn’t be a bad idea.

“I found Los Angeles County’s approach very prudent,” said Dr. John Swartzberg, professor emeritus of infectious disease and vaccinology with the UC Berkeley-UCSF Joint Medical Program. “The United States right now is an island from what the rest of world has experienced in the last few weeks. I’m not sure how long that will last. I think Los Angeles County is doing the right thing telling people to be a little more cautious and add another weapon beyond just being vaccinated.”

In making its recommendation, the Los Angeles County public health department cited concern about the highly contagious Delta variant that ravaged India this spring and has spread like wildfire around the world and across the U.S. In a statement the health department noted that the variant was present in nearly half of virus cases sequenced in the county. On June 15, California officially lifted restrictions on gatherings and activities amid falling infection rates. But cases of the Delta variant have started to pop up, putting health experts on alert.

“Until we better understand how and to who the Delta variant is spreading, everyone should focus on maximum protection with minimum interruption to routine as all businesses operate without other restrictions, like physical distancing and capacity limits,” Los Angeles County Public Health department said.

Studies have shown Pfizer and Moderna vaccines to be effective against the Delta variant. But the variant has alarmed leaders around the world given the speed at which it can spread. The World Health Organization last week noted that it is in 85 countries, spreading rapidly among the unvaccinated and, with easing public health restrictions, is accelerating even in highly vaccinated countries such as Israel, England and the U.S. The U.S. Centers for Disease Control and Prevention says it now accounts for one in five new infections in this country, up from one in 10 a week ago.

The WHO last week said vaccines alone won’t stop the virus’ spread and urged even immunized people to continue wearing masks and distancing from others.

But the CDC hasn’t altered its guidance from mid-May, that the vaccinated don’t need masks outdoors or most indoor settings, with a few exceptions for public transportation, medical and correctional facilities, shelters and school buildings.

And California, which waited a month before adopting the CDC’s mask guidance, said it sees no need to shift course. State Public Health Officer Dr. Tómas Aragón said Tuesday that local health authorities are free to impose stricter guidance and noted that unvaccinated individuals are still required to wear masks around others.

“The most important thing we can do to stop the spread of COVID-19 is ensure everyone who is eligible gets vaccinated,” Aragón said.

In the virus-wary Bay Area, where public health restrictions have enjoyed strong support and masks remain plentiful despite high vaccination rates, many people weren’t waiting around for a new health department recommendation.

“I think that we should mandate masks in public areas,” said retired teacher Kathy Ramirez as she walked through downtown Sunnyvale with a mask. “I’m very concerned that people aren’t taking this seriously.”

Azura Gao, who moved to the Bay Area from Los Angeles two weeks ago, agreed.

“I see more and more people coming out and not wearing masks,” Gao said. “But for myself, I’m very cautious. I think it’s better for us to wear a mask.”

Santa Clara County public health officials said Tuesday that given high vaccination rates, there’s no need for a broader mask rule.

“While we recognize that masks are effective in reducing transmission and are especially valuable in crowded, poorly ventilated indoor spaces, at this time, we are not reimposing a community-wide masking requirement,” Santa Clara County’s public health department said Tuesday.

Santa Cruz County health officials announced Tuesday that a man in his 50s who said he had been vaccinated had become ill with the Delta variant and was experiencing mild symptoms. The health officials urged the unvaccinated to get the shots rather than imposing masks for those already immunized.

“With the reopening of the economy and slowing vaccination rates, the introduction of a highly transmissible variant creates an especially worrisome situation,” said Santa Cruz County Deputy Health Officer Dr. David Ghilarducci. “For those who are unvaccinated or only partially vaccinated, your risk of serious illness is becoming more likely. The best way to reduce the risk for everyone — including residents not yet eligible to be vaccinated — is to seek a vaccine as soon as possible.”

Other health experts agreed Tuesday.

“There is no reason to change our mask guidance for the Delta variant, as the vaccines are still effective against the Delta variant,” said Dr. Monica Gandhi, an infectious disease specialist at the University of California-San Francisco.

But Dr. Bob Wachter, who chairs the UCSF medical department, said Monday on Twitter that troubling reports of “Delta-fueled upticks” in infections in highly vaccinated Israel and the United Kingdom have led him to resume wearing masks indoors unless he’s sure others are vaccinated like himself.

He said Tuesday that while a new mask order is premature, L.A. County’s recommendation is reasonable.

“I think it’s fine for them to recommend, but not mandate, that vaccinated people consider wearing their masks if they are unsure of the vaccine status of others sharing the space,” Wachter said. “But if we see a significant uptick in cases in the Bay Area, then I think reinstituting an indoor masking mandate would be appropriate.”