The rate of new coronavirus cases in Philadelphia has increased sharply in recent weeks, the city’s top health official warned Tuesday as she urged residents to wear masks and get vaccinated — but she stopped short of instituting a mask mandate or restrictions on businesses and events.

While acting Health Commissioner Cheryl Bettigole did not rule out the possibility of future restrictions, she said city officials hope to minimize changes in rules or guidance.

“Our commitment is to keep Philadelphians safe but also to keep the restrictions to the minimum that’s necessary for that safety,” she said. “We are not looking to make people’s lives miserable. So we’ll try to do what’s necessary but to minimize restrictions where possible.”

Bettigole’s renewed warnings came just two months after the city fully reopened, lifting its mask mandate and all other coronavirus restrictions. Cases have risen nationwide in recent weeks, driven by outbreaks in states where vaccination rates are low.

The rate of new cases in Philadelphia doubled between July 12 and July 19, and doubled again between July 19 and Aug. 1, Bettigole said.

» READ MORE: Philly region seeing a ‘substantial’ spread of COVID-19, expanding the area where indoor masks are recommended

COVID-19 case rates in Philadelphia are about as high as they were last summer, and still much lower than at the worst points of the pandemic. But she said the rise is cause for concern and means the pandemic “has taken a turn that none of us wanted to see.”

That increase prompted the city to issue a guidance in late July recommending mask use indoors for all residents, regardless of vaccination status.

Bettigole also recommended Tuesday that residents avoid crowded indoor gatherings, and said it is “probably a good idea” to wear a mask at crowded outdoor events where people are packed together, such as concerts or Phillies games.

The updated mask guidance issued last week by the U.S. Centers for Disease Control and Prevention classifies Philadelphia and several surrounding counties as having “substantial” transmission, meaning masks are recommended indoors. Bucks, Montgomery, and Delaware Counties also have “substantial” transmission, according to the CDC, as do nearly all counties in New Jersey.

That new guidance came as new CDC data indicated that the delta variant of the coronavirus spreads as easily as chicken pox and could be spread by vaccinated people just as much as by unvaccinated people. But vaccinated individuals are still less likely to get severe illness, be hospitalized, or die.

» READ MORE: The delta variant may spread as fast as chickenpox, and other facts about new CDC data

Bettigole said the health department will continue “following the science day to day as it changes” to determine if other changes in guidance are needed.

“One of the things we’ve all learned with this pandemic is that things we know today change tomorrow,” she said. “And that’s been true again and again.”

Philadelphia has so far stopped short of measures enacted in other states and cities, such as requiring vaccines for government workers or mandating verification of vaccination status to dine indoors or go to a gym — as New York City announced Tuesday.

“I don’t want to take anything off the table, but it’s certainly not top of mind for a next step,” Bettigole said of New York’s move.

Bettigole said it could be challenging and confusing to have a patchwork of different systems for verifying vaccination status in Philadelphia and its surrounding counties.

Philadelphia officials are, however, still considering whether to require vaccination for city workers.

» READ MORE: Some cities are requiring government workers to be vaccinated. Philly isn't — for now.

Mayor Jim Kenney said Monday that his administration is “looking at all options available.” Bettigole said no final decision has been made.

“The conversations about vaccine mandates take some time to have, in terms of what that looks like, who we need at the table,” Bettigole said. “We can’t declare it today unless we know how we’re going to do it.”

Individual businesses can choose to require masks or vaccination for employees or guests if they decide to do so, Bettigole said.

The city is also working on ways to encourage unvaccinated residents to get a shot, Bettigole said, including a plan to follow President Joe Biden’s suggestion that local governments offer $100 to residents as an incentive to get vaccinated.

About 76% of adult residents have now received at least one vaccine dose, and 62% are fully vaccinated.

» READ MORE: Full list of Philadelphia restaurants that require proof of vaccination

The rate of new cases is rising fastest among young people, who also have the lowest vaccination rates in Philadelphia.

City data show that in the age range of 18 to 44, 30% of Black residents have had at least one dose, along with 52% of Hispanic residents, 53% of white residents, and 79% of Asian residents.

Bettigole said Philadelphia’s hospitalization rates have not risen as steeply as new cases, but she noted that she has heard stories from colleagues across the country about people in their 20s who are hospitalized and on ventilators.

“I think young adults have felt pretty safe through this,” she said, “and that is not as true as we would like it to be.”