The Alembic, a cocktail bar and restaurant in San Francisco, was part of the first wave of businesses to require workers and patrons to be vaccinated against Covid-19 when it restarted indoor dining in June.

Co-owner Kathryn Kulczyk said backlash from the public was swift and much of it came through Alembic’s page on Yelp , the popular reviews site.

“People were calling us Nazis,” she said. “Saying that we supported the devil because we wanted proof of vaccination.”

In early August, Yelp Inc. added features allowing businesses to list their vaccine policies on their pages, just as they could advertise that they deliver or accept credit cards. There are two new settings: A business can indicate if its staff is fully vaccinated against Covid-19 and if it requires patrons to provide proof of vaccination; users can filter their search results based on those options.

The change has thrust Yelp—and the small businesses listed on its pages—into the broader debate over vaccine requirements. The San Francisco company has beefed up moderation to manage what it calls “review bombings,” instances where public attention to a business results in an influx of negative reviews from users who aren’t necessarily customers.