All Pennsylvanians 16 and older are eligible to sign up for coronavirus vaccine appointments beginning Tuesday, six days earlier than the state had previously planned, Gov. Tom Wolf announced Monday.

The decision came after vaccine providers across the state reported difficulty filling appointments, officials said, now that the supply of the vaccine has increased and more than a third of the state’s population has already gotten one or both shots.

“We realized the need to keep the demand at its highest [level] possible was incredibly important,” acting Health Secretary Alison Beam said at a news conference. “That’s why we progressed to phase 2, to allow us to sustain that demand which can keep the pace of the vaccinations up.”

The new timeline does not affect Philadelphia, which has its own vaccine distribution plan. City officials said they would stick with their plan to open eligibility to all adults on April 19. In much of the suburbs, all residents 16 and older were already free to make appointments: Chester and Bucks Counties opened eligibility to all on Friday, and Montgomery County did the same Monday.

The state’s decision also came as health officials grow increasingly concerned about new spread of the virus and its variants. Pennsylvania’s seven-day average for the number of new daily cases was 4,236 as the week began, up from a post-surge low of around 2,400 cases a day in early March. The statewide percent of positive COVID-19 tests has also begun increasing — from around 6% at the end of February to 9.5% last week — as has the 14-day moving average of the number of daily hospitalizations, the Health Department said.

Beam said it was a “vaccination vs. variants” situation and urged even those who have been inoculated to continue following safety measures that protect against the virus’ spread.

» READ MORE: More transmissible coronavirus variants on the rise in Pa. and N.J., as case counts keep going up

“We need to maintain acceleration of the vaccine rollout, especially as case counts and hospitalization rates have increased,” Wolf said in a statement.

Declaring April would mark a “critical turning point in this pandemic,” Beam noted that Pennsylvania was again ranked 11th among states for the percentage of residents who have gotten at least one dose. In spite of the need to open eligibility to fill appointments, she said demand for the vaccine remains high.

» READ MORE: Pa. is finally expanding vaccine eligibility. But perceptions of a rocky rollout linger.

“It’s a good sign,” she said, “because the more people who are vaccinated means the faster we can stop the virus.”

She did not specify in which regions of the state providers were having trouble filling appointments.

The state requires providers to use 80% of their first doses within a week of delivery, Beam added, and some reported they were having trouble meeting that benchmark in recent days.

The state began expanding its eligibility two weeks ago, as frontline workers became eligible and all adults in the state’s 1B group joined last week. People in phase 1A — which includes those 65 and older, people with high-risk conditions, health workers, and nursing home residents and staff — also remain eligible.

The 1C phase, which includes a broad list of workers, opened Monday. Universal adult eligibility had initially been set to follow a week later, on April 19, the date by which President Joe Biden has directed all states to open eligibility to the general public.

So far, Pennsylvania has administered more than 6.4 million coronavirus vaccinations to more than 4.2 million people, or nearly 39% of its eligible population. More than 2.4 million residents are fully vaccinated.

In New Jersey, where all adults 16 and over will be eligible April 19, 42% of residents have gotten at least one shot, ranking the state seventh. Gov. Phil Murphy said Monday that more than 75% of the state’s over-65 residents have received at least one dose, and 3.4 million people in total have had one dose or are fully vaccinated. The state’s goal is to vaccinate 4.7 million people — about 70% of the adult population — by the end of June.

With supply of the one-dose Johnson & Johnson vaccine expected to be lower in New Jersey, Pennsylvania, Philadelphia, and nationwide over the next few weeks while the company resolves manufacturing issues, New Jersey Health Commissioner Judith Persichilli urged residents not to wait for a specific type of vaccine.

“Please take whatever vaccine is available,” she said. “Please take the first opportunity you have to be vaccinated.”

For Pennsylvania, reaching the vulnerable 65 and older population, some of whom aren’t tech-savvy and had trouble getting appointments earlier in the rollout, remains a priority, officials said Monday. As of Friday, federal data showed Pennsylvania had fully vaccinated 54% of seniors aged 65 and over, and 84% have had at least one shot.

» READ MORE: Pa. seniors are ‘at their wit’s ends’ trying to get coronavirus vaccines

The region’s Area Agencies on Aging will keep helping providers, they said, and other equity initiatives will continue.

Beam, other officials, and community leaders in Harrisburg announced a statewide vaccination and education tour, including a mobile van that will administer shots in communities of color and other historically underserved areas.

Similar, more localized efforts are underway in areas across the state. Chester County is already planning door-to-door efforts in Coatesville and at the county’s 70 mobile-home communities to reach low-income or Black residents who may be hesitant about getting the shot or face transportation barriers, said county health director Jeanne Franklin. Eventually, she said, they plan to bring mobile vaccine clinics into these areas, allowing people to get vaccinated on the spot.

Delaware, Chester, and Bucks County residents can sign up on their counties’ websites, where available appointments are released regularly, and no longer need to preregister. Montgomery County residents can register online or by phone; appointments are being released randomly, not in the order in which people sign up, but are prioritized by phase.

Expanding eligibility will allow counties to gauge the level of vaccine hesitancy more quickly and to better target education and outreach efforts, said Franklin. Chester County, she said, was not among those struggling to fill appointments.

» READ MORE: As Americans scramble to get vaccinated, many rural, conservative Pennsylvanians feel no urgency

In the coming weeks, she said, they should reach a point where everyone who wants a vaccine has gotten one. From there, the county will ramp up its mobile outreach and its work with community partners.

Even accounting for hesitancy, Franklin said she sees an end in sight for this initial, large-scale effort.

“We don’t anticipate doing this level of vaccination through the end of the year,” she said. “I’d like to see it wrapped up in June, July. And then we’re preparing for what the fall looks like.”

Data journalist Chris A. Williams contributed to this article.