Starting Wednesday, hospitals and nursing homes in California must verify that visitors are vaccinated or have tested negative for the coronavirus within the last three days — the Golden State’s latest COVID requirement amid a pandemic with no end in sight.

The shift could offer another indication of things to come as hospitals pivot from screening visitors for symptoms to checking vaccination cards and QR codes. With the delta variant surging across the state and employers from Facebook to the federal government now mandating workers get vaccinated, an increasing number of businesses from bars to concert halls are barring the unvaccinated.

Is California finally on the cusp of adopting a vaccine passport?

“I think the conversation has shifted to these two words that we didn’t want to use at the beginning,” said Monica Gandhi, a UCSF infectious disease expert, “which are vaccine passports and vaccine mandates.”

It’s been months since the idea of vaccine passports first surfaced and then quickly ran into opposition. Critics worried about privacy issues and complained a passport infringes on personal freedom. As COVID cases plummeted in the spring and the state reopened in June, talk of a passport all but disappeared. Then came last month’s delta surge. Prominent Republican candidates in the upcoming Sept. 14 recall election have said they do not support vaccine mandates and Gov. Gavin Newsom, battling to keep his job, has so far avoided endorsing the idea of a vaccine passport even as the state slowly requires more sectors to verify vaccination status.

But there are signs California’s private sector isn’t waiting. After a slow start, downloads of a free app that allows users to verify California residents’ vaccination status through QR codes are on the rise.

“It’s definitely picked up in the last two weeks pretty substantially,” said JP Pollak, co-founder of the nonprofit Commons Project, which helped develop a health card framework being used by a range of companies and organizations across the country, from Walmart to UC Health.

But unlike in New York, where residents can use a vaccine passport called the Excelsior Pass, the Golden State doesn’t have one standardized way for checking or displaying vaccination status, leaving residents navigating a patchwork of options. That could change, with some health experts predicting a passport is all but inevitable once the vaccines are fully approved by the U.S. Food and Drug Administration, a stamp of approval that could come in weeks.

Gandhi was visiting New York this week and experiencing first-hand living in a vaccine passport world.

“I can’t get in anywhere without showing the card,” said Gandhi, who was carrying the Centers for Disease Control and Prevention (CDC) paper card she received when she got her shots but likes the idea of California or even the U.S. having a vaccine passport.

When she went out to dinner for her birthday at Restaurant ANZU in San Francisco earlier this month, she said, the restaurant, which informs diners on its website that they should be prepared to show proof of vaccination, was scanning QR codes and checking paper CDC cards before allowing people to eat there.

The opposition, Gandhi said, reminds her of the days when restaurants started created smoking sections and eventually banned indoor smoking altogether. Smokers initially chafed, but the rules stayed and eventually fewer people smoked. Gandhi thinks if more places require vaccination, vaccine holdouts who have not been swayed by cash prizes or scientific reasoning may opt to get jabbed.

In the meantime, different places in California, either by choice or to comply with ever-shifting state guidance, are making different decisions about how to check vaccination status.

Chuck Cole, the chief operating officer of Chaparral House, a nursing home in Berkeley, said his team has been asking visitors to show proof of vaccination for months. They tell visitors to bring their CDC card, make a copy and make a note that the person is vaccinated in their system so they don’t have to repeat the process each time. He personally thinks the idea of a passport is “fabulous” but is skeptical it will happen with disagreements about who should have access to the information and how it should be stored.

The lack of consensus, he said, “makes it difficult.”

California’s hospitals, which have seen the number of COVID patients nearly double to more than 5,000 in the last couple of weeks, are bracing to start screening Wednesday for the variety of ways the state says visitors can show they are vaccinated, from the CDC card to a QR code.

John Muir Health in Contra Costa County said it will ask patients and visitors to show proof of vaccination using any of the options the state has endorsed, but may make exceptions when a patient is in critical condition and nearing the end of their life.

Sutter Health will take a similar approach, sending an email to members this week warning that nearly all visitors, including partners supporting patients in labor, will be subject to the new requirement. “Please plan accordingly if you’re expecting a baby,” the note said.

Steve Yoshifuji, a 68-year-old from San Mateo, came to El Camino Health’s Mountain View hospital Tuesday for his wife’s surgery. A greeter asked him whether he got vaccinated as they walked in, but he didn’t have to show proof. That will change Wednesday.

“That’s fine with me. I mean, I got vaccinated,” Yoshifuji said “It’s good. I don’t get why people aren’t getting vaccinated.”