In a sign of things to come in San Francisco, Zuni Cafe announced that it is going to begin requiring not just full vaccination but also proof of a booster shot for indoor dining starting next week.

"We remain disinterested in invading your medical records and we have a strong desire to keep the guests and workers of Zuni Cafe safe," the restaurant said in a Tuesday Instagram post. "We look forward to a time when this will not be necessary."

It's already been widely documented that as Omicron spreads, those whose immunity from two vaccine shots has begun to wane are highly vulnerable to infection — and even boosters don't offer 100% protection, but the protection against infection and serious illness appear to be quite high. That has led to booster mandates for healthcare workers at the state level, and a proposed booster mandate for all city workers in San Jose.

At Zuni, those who are not yet eligible for boosters, because their original vaccine series was less than six months ago, will be able to show documentation of that in order to dine indoors. But otherwise, starting December 29, the restaurant will be requiring a scannable state vaccine record or a photo of their vaccination card showing the three doses.

Diners without such proof will be asked to dine outdoors.

San Francisco has been requiring proof of full vaccination for entry into bars and restaurants since August 20. But experts have been warning for at least two months that "full vaccination" would be soon defined as three shots. And many employers around the country have already instituted mandates for boosters.