San Francisco will require indoor customers of restaurants, bars or gyms to provide proof of full immunity, making it the first large city in the United States to implement such strict rules.

Mayor London Breed's office said in a statement on Thursday that the rule would also apply to large indoor spaces, such as theatres and entertainment venues.

Last year, San Francisco was one of the first outbreaks in the United States, and the number of cases in the area is now rising again because of the spread of the Delta variant. New York City implemented a similar rule last week, but only requires customers who eat in restaurants and gyms to get a dose of the vaccine.

San Francisco and surrounding counties re-imposed mask orders on public indoor places last week, regardless of whether indoor workers have been vaccinated or not.