Lehigh County could not open any new vaccine clinics this week. Chester and Allegheny Counties did not receive any additional first doses to administer. And after Monday, Montgomery County’s clinic could run out of the coronavirus vaccine completely.

The four counties — among Pennsylvania’s most populous — each received far fewer vaccine doses than expected from the state this week, slowing distribution and reflecting a problem that plagues the vaccine rollout every week at both the state and local level: not knowing how many shots will actually arrive.

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“We can’t plan for the future when we don’t know how much we’re getting,” Allegheny County Health Department Director Debra L. Bogen said at a news briefing this week.

Even as the national supply of vaccine increases — starting this week, all states were expected to receive 22% more doses than they had before the Biden administration took office — the Pennsylvania Department of Health said the state’s vaccine supply, allocated by the federal government, is simply very limited.

That in turn constrains counties’ ability to plan and register appointments, creating the short scheduling window that has frustrated many residents. No one wants to offer appointments, then cancel because of a shot shortage.

“The solution,” said spokesperson Barry Ciccocioppo, “is a larger supply of vaccine.”

Still, the shortage in the affected counties was striking.

Allegheny County, which includes Pittsburgh, received only 1,000 doses, enough to cover its scheduled second shots but not to allow the county to expand appointments, she said. (Giving the time-sensitive second dose to someone who has already received the first of the two-dose shots is a priority.)

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The 1,000 first doses delivered this week to Montgomery County were 3,500 fewer than last week, and some county hospitals also reported smaller deliveries, Commissioner Val Arkoosh said.

“This week is a perfect example of the supply challenge that we are dealing with,” Arkoosh said Wednesday. “We were told yesterday that we would receive a delivery of vaccine today, but we were not told how many doses would be in that delivery.”

With its reserve supply, that’s enough for Montgomery County’s clinic to operate through Monday, although that includes two days of shots that would have already been given out if not for the snowstorm delaying appointments.

Chester County didn’t receive any of the 5,000 first doses it requested but got the 3,200 second doses it asked for, according to a county spokesperson.

It was unclear Thursday whether other counties were experiencing the same unwelcome surprise: A state spreadsheet that normally shows how many doses each provider receives weekly had not yet been updated for the week. The Department of Health said it had not been updated due to a staff absence.

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Ciccocioppo, its spokesperson, said the state’s vaccine supply was spread more thinly this week because more providers are ready to vaccinate patients than in previous weeks. Providers across the state asked for more than 705,000 doses this week, while the state had only 166,000 to give out.

“We are working to stabilize the distribution as best we can while also trying to get vaccine into more areas of the state,” Ciccocioppo said.

He said he could not say whether the trend would continue next week or beyond because the state does not yet know how much vaccine will be coming from the federal government.

The weekly vaccine deliveries have been unpredictable nationwide from the start. As officials have stressed there simply aren’t enough doses yet for everyone to be vaccinated at once, critics have questioned the pace at which Pennsylvania’s available shots are getting into people’s arms.

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Statewide, more than 2.1 million vaccine doses will have gone to providers by Friday, and the state estimates nearly 881,000 first doses and 230,000 second doses will have been administered. That will mean 52% of the state’s shots have been given out, a rate that many states are outperforming and about which state lawmakers pressed the Department of Health at a hearing Thursday.

Gov. Tom Wolf said Thursday that even with the federal supply issue, Pennsylvania could be doing better.

“We have a system in place,” he said. “We need to continue to figure out how we can make it much, much better.”

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At the hearing in the Pennsylvania Senate, lawmakers pressed acting Health Secretary Alison Beam about what they see as a lack of transparency and expressed frustration over the pace of distribution.

State Sen. Maria Collett, a Democrat representing parts of Montgomery and Bucks Counties, cited Montgomery County’s low allotment this week, telling Beam she was “beyond frustrated” with the rollout.

“Your claims of accountability — I’m sorry to say that I am having a difficult time trusting that that is actually happening,” Collett said. “I have not heard a lot about logistics from yourself and from the department this morning. ...What is the plan moving forward to do better?”

Beam said the state was committed to getting all vaccine recipients their second doses on time, and said the Department of Health would begin meeting weekly with the legislature.

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On the county level, officials struggled to plan.

“If we don’t receive more in time for Tuesday,” Arkoosh said, “we will not be able to offer vaccines on that day.”

Lehigh County received only 1,000 doses, almost all of which are for second shots, said Vicky Kistler, director of the Allentown Bureau of Health, which serves all of Lehigh County.

“It’s frustrating because we have the capability right now to do more,” said Kistler, noting their clinic could give shots to 1,200 to 1,500 people in a single day.

Kistler said commonwealth officials have “been very clear” that they are distributing as much as they can, so there’s not much else the health bureau can do except be patient and see what next week brings.

The hardest part, she said, is not knowing whether the trend will continue. The county has told the commonwealth they are ready and willing to take more. But, she said, “we accept what we get.”

Graphic artist Chris Williams contributed to this article.