San Francisco's new rule requiring proof of full vaccination to enter bars, nightclubs, theaters, gyms, and restaurants takes effect today, and some restaurants are expecting some awkward situations to arise.

As of last month, hundreds of bars across the city already began requiring proof of vaccination to enter, just as the Delta variant surge was gripping the city and proving even moreso that vaccines were necessary — with even some who are vaccinated getting mildly sick with COVID. But now the rule is coming from the city's health department, and there are stringent rules attached requiring vaccine checks at the door for restaurants, gyms, and theaters, too — and no more honor system.

San Francisco is the first major city to go this far with its vaccine mandate for the public — New York City is only requiring proof of a first vaccine shot, and New Orleans is requiring either vaccination or proof of a negative COVID test for bars and restaurants only.

"There's definitely some anxiety around how it's all going to work," says Pete Sittnick, a managing partner of Waterbar and EPIC Steak restaurants, speaking to ABC News this week. "The good thing is, if somebody doesn't have their verification of vaccination they can still eat outside. There is an option and we just need to be ready for different scenarios."

Pearce Cleaveland, co-owner of the Temple nightclub, tells ABC News that his door staff has already been trained, and the process has been going just fine.

"We’ve had people who get upset at the door when they’re turned away, but in general they’re understanding,” he said. “It’s the tourists who are generally disappointed, when they’re unaware of the requirement and can’t get vaccinated quickly enough."

San Francisco is also requiring all workers at these businesses to be fully vaccinated, but they have until October 13 to complete their vaccines.

"This new health order is about protecting the health of employees, residents, and visitors, and keeping our businesses open," Mayor London Breed said when the announcement was made last week.

One easy way to show proof is to snap a screenshot of your digital vaccine card, which you can access here. Businesses will also accept clear photos of your paper card.

Some businesses, like music venue The Independent, are specifically asking ticket holders to download an app for vaccine verification — The Independent has been using Health Pass by CLEAR.

Also, be aware that most of these businesses are also requiring masks to be warn indoors when not actively eating or drinking — though enforcement of this rule has been fairly lax at many bars.

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