While many parts of the world are shedding isolation requirements and mask mandates, public health authorities in Philadelphia appeared to be bucking the trend.
But four days after the city of 1.5 million people became the first in the United States to bring back mask-wearing indoors, it has done a lightning-fast reversal.
"We don't feel like the mandate is necessary at this point," said Philadelphia Health Commissioner Cheryl Bettigole during a press conference.
"I think what we've seen is Philadelphians paying attention to public health and doing what they needed to do."
In February, following a spike in coronavirus cases, the Philadelphia Department of Health came up with a simple test to decide when to ease or tighten the rules.
It was a bid to do away with unpredictable restrictions, using a formula that balanced daily case numbers, the pace of spread, and hospitalisations.
But, in practice, the automatic trigger created a thornier set of problems, with some small business owners experiencing whiplash.
Personal trainer Justin Taylor is among those whose business revenue collapsed after prolonged closures due to the coronavirus.
Until January, he and his business partner rented a boutique gym but received an eviction notice after being unable to keep up with mounting bills, including rent.
"Everybody was kind of scared to come into the gym," Mr Taylor said.
He is now back in his element training clients in a borrowed industrial shopfront down the block from his old spot.
He said the will-they-won't-they COVID rules have made it hard to feel secure.
"I think everybody was kind of relieved once we heard that the mandate was lifted," he said.
"But it does kind of put us in a situation where we're uncomfortable and we're not sure of whether or not we're going to have to change our entire business plan out of the clear blue or if we're going to continue.
"We never know if … our business plan right now is going to work for the next pandemic, or the next time they call [for] masks.
"It's like this rollercoaster of staying aware and being conscious of the numbers and the strains and what the government is saying, and the protocols that we have to follow as businesses."
Did the Philly formula fail?
COVID-19 cases peaked in Philadelphia in January, averaging about 4,000 cases per day as Omicron ripped through the population during winter.
In response, the health department, with input from the business community, set up a metrics-based system to help manage future waves of the virus.
This included the three-pronged test that caused the indoor mask mandate, which was dropped in March, to kick back in last week when daily cases surpassed 100, with a troubling growth rate of more than 50 per cent over 10 days.
Philadelphia moved from level one, "All Clear", to level two, "Mask Precautions", because two out of the three metrics were exceeded.
"We were trying to make it predictable and understandable for people," Dr Bettigole told the ABC.
"It's less political in Philadelphia than it is in some other places in the US."
According to Dr Bettigole, the goal was to uncouple a rise in case numbers from a flow-on increase in hospitalisations and ease pressure on overstretched health services.
She defended the quick turnaround on masks on Friday, telling reporters the "warning sign" had worked as intended.
"[When] we started to see that increase in cases, we put the mask mandate into place to make sure that we could head off an increase in hospitalisations if one was going to happen," she said.
"And we said at the time that if we didn't then see an increase in hospitalisations that we needed to rethink, and that's exactly what we're doing.
"So it really is consistent. We're doing what we promised to do."
Daily case numbers are well below the January peak but Dr Bettigole said the city was right to be cautious.
"I feel like we had a sort of national decision that the pandemic was over," she said.
"Sadly, we don't get to decide that."
Many Americans are going mask free
All levels of government in the United States have grappled with when to introduce COVID-19 restrictions, with cities seesawing between harsh and lax rules as cases rise and recede.
Earlier this week, a video posted on social media showed passengers celebrating on a domestic flight after a Florida judge quashed one of the last remaining national mask mandates, covering airplanes and other public transport.
US district Judge Kathryn Kimball Mizelle — a controversial Trump appointee — ruled the Centers for Disease Control and Prevention (CDC) had exceeded its authority by setting the rule.
The decision is now being appealed by the Department of Justice and could yet be reversed before it expires in May.
Meanwhile, the White House has sought to project optimism about the outlook for the disease.
"If the infection numbers are relatively low, as they are right now, then I think it's reasonable to remove mask mandates," said Dr Ashish Jha, a COVID response coordinator for the Biden administration.
Dr Bettigole said while the national picture might be looking rosier, she is firmly focused on protecting Philadelphians.
There's no one-size-fits-all solution
Of the 25 largest cities in the United States, Philadelphia has the highest percentage of residents living below the poverty line, making them more vulnerable to fluctuations of the virus.
"We have a more vulnerable population," said Abby Rudolph, an infectious disease and social epidemiologist at Temple University.
Dr Rudolph had backed the city's decision to bring back mask mandates, calling it an "act in the common good".
But the determination of the public good is not an exact science.
Patti Brett is the owner of Doobies Bar, a Davie Bowie-themed dive bar that has been open for decades.
She struggled to stay afloat throughout the pandemic and the bar closed several times in line with the city's restrictions.
Ms Brett said she was also worried about her and others' health.
"I just didn't feel comfortable letting people in here," she said.
Ms Brett is sympathetic to the balancing act the city is trying to perform and plans to request vaccination records from her patrons, even if it puts some offside.
Like Mr Taylor, she is uncertain about the future.
"I still don't know if I'm going to make it."
