For six weeks, it was just like old times at Four Moon Tavern in Chicago's Roscoe Village neighborhood.

No masks. Few worries. Little of the preoccupation that has hung over the last 1½ years of pandemic living.

But last week, a vaccinated staff member at the bar tested positive for COVID-19. Four Moon co-owner Robbie Lane didn’t hesitate over what to do next: she closed Four Moon for two days and reopened Thursday with a renewed mask mandate and a requirement that anyone sitting at the bar show proof of vaccination. Lane said she is still weighing whether to make the entire bar open only to vaccinated customers.

“I know how tired we all were of wearing masks, and it was really nice to let that go for a while,” she said. “But it doesn’t feel like things are going in a good direction.”

As COVID-19 cases spike in and around Chicago due to the highly contagious delta variant, restaurants and bars have swiftly reexamined protocols and procedures without waiting for government mandates, especially as so-called breakthrough cases among vaccinated people emerge.

More are likely to follow, especially after Chicago began recommending everyone older than 2 years wear masks indoors.

Some are reverting to safety measures of recent months, including returns to mask mandates and social distancing. Others are temporarily closing due to positive cases on staff or moving to allow in only vaccinated customers.

But even those with vaccine mandates are running into trouble: Spanish-inspired restaurant mfk, which has only admitted customers with proof of vaccine since reopening in late June, announced Friday it would close indefinitely after a vaccinated staff member tested positive following a revelation that three vaccinated customers who dined at mfk Sunday also tested positive.

“I don’t know what’s going to happen with the restaurant right now,” mfk owner Scott Worsham said. “From a business standpoint, it is quite devastating.”

He said he’s thankful he decided to open the restaurant only to vaccinated customers, and will continue to do so.

“We are definitely still a vaccinated-only restaurant,” Worsham said. “Getting the variant while vaccinated has been proven time and again to be far safer than getting infected without being vaccinated, right?”

The Lakeview restaurant’s announcement came amid a flurry of bars and restaurants changing gears Friday. Nearby, Delilah’s in Lincoln Park closed for a few days after it said Friday multiple vaccinated staff members tested positive.

Humboldt Park bakery and soda fountain Spinning J announced Friday it is once again closing indoor service. Its dining room had reopened in early June after 14 months closed.

“With so many breakthrough cases being reported by friends and colleagues, it just doesn’t make sense to expose even our fully vaccinated staff unnecessarily,” Spinning J said in a social media post. “This was not an easy decision to make, but with so many events and festivals in town this weekend, I want to protect our little pod of pastry people as much as possible.”

Humboldt Park deli Jeff & Judes announced on social media Friday it would also close after a vaccinated staff member tested positive for COVID-19. In an Instagram post, the deli urged people to get vaccinated and to “continue masking indoors because this delta variant is no joke.”

When Jeff & Judes reopens, probably next week, it will be with a masking policy the restaurant had been relieved to drop in late June, once staff members had all been vaccinated, said chef and owner Ursula Siker.

In recent weeks, Jeff & Judes allowed vaccinated customers to skip masks inside the restaurant, but without showing proof of having been vaccinated, which Siker said “was a naive choice on our part.”

Open until this week for counter service and outdoor seating, Jeff & Judes is building an indoor dining area that Siker had hoped to open in October. She said she can’t fathom what restrictions she may need to institute — or whether she’ll even be able to seat people indoors this fall.

“We’ll have to make some tough choices about letting guests inside,” she said. “To feel like we’re launching back into tighter restrictions will be hard, but most important is staff feels safe and guests feel taken care of.”

Several businesses have announced in recent days they will only permit customers who show proof of vaccination, including Hydrate Nightclub, Berlin Nightclub and Pilsen bar Skylark, which said simply on Facebook Friday, “Only fully vaccinated people are now welcome at the Skylark.”

Logan Square’s Cole’s Bar, which already required proof of vaccine, returned to a mask mandate Friday. City Winery said Thursday it would require patrons to wear masks.

Lane, of Four Moon Tavern, said the six weeks of running her 22-year-old bar like the pre-pandemic days were a relief. The first night of normalcy, when the city and state eased all restrictions for indoor eating and drinking June 11, was surreal, she said.

“About 10:30 that night, I just looked around and thought, ‘It looks like nothing ever happened.’ People were playing pool, it was busy and people were having fun,” she said. “It was a little shocking, but it also felt good. I definitely had mixed feelings about it, though, because you’re a little afraid of what might happen.”

Now, she said, she’s back to checking the city’s COVID-19 statistics every day, which she had stopped doing earlier in the summer.

She’s also preparing for the occasional pushback from customers about masks and showing vaccine cards to sit at the bar.

“I expect it might happen, but that’s how we’re going to do it and sorry — either get on board or move along,” she said.