SAN FRANCISCO — Greg Ryken showed up to his favorite lunch spot in San Francisco on Friday with an appetite and his vaccination record in hand.

A manager at Sam's Grill and Seafood restaurant verified he was fully vaccinated against COVID-19, put him on a list of customers who have met the city's new requirement for future reference, and walked him to his table.

“Easy,” Ryken said as San Francisco became the first major city in the U.S. to enforce the strictest vaccine mandate for entering restaurants, bars, gyms and large concerts.

Businesses posted signs and added extra staff to begin verifying people's vaccination and identity cards before allowing them in.

“We tested systems in place to see how we would do it; we were talking to our customers, getting our staff prepared, and we are so thrilled to have the full-throated support of the leadership of our city so we can confidently walk into this new landscape together,” said Tracey Sylvester, owner of a Pilates studio in the Mission neighborhood.

Pete Sittnick, a managing partner of Waterbar and EPIC Steak restaurants on the city's waterfront, said he was worried about slow check-ins, resistance from guests against the requirement or people showing up without proper documentation. So far, he said, the lunch crowd came with vaccination cards in their hands, and the line to get through the door was short.

“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,” he said.

Mayor London Breed announced the requirement more than a week ago in an attempt to stem rising COVID-19 cases, saying she was worried the highly contagious delta variant could disrupt the city's economic rebound. She also hopes it will encourage vaccine holdouts to join the 79% of the population that have gotten their shots.

The mandate goes further than New York City, which requires people to be at least partially vaccinated for a variety of high-risk indoor activities, and New Orleans, which requires proof of vaccination or a negative COVID-19 test for indoor dining or drinking. All three cities make exceptions for people who don't qualify for the vaccine, including children under 12.