Pennsylvania’s former health secretary returned to the state Thursday to observe federal efforts to vaccinate Philadelphians, but rows of empty chairs at the Convention Center suggested the time for mass vaccination sites may be passing.

“There’s always this tension between mass vaccination sites, but then vaccination that you need to target toward specific groups for health equity,” said Rachel Levine, now assistant secretary for health at the U.S. Health and Human Services Department. Levine, who is a pediatrician, left her position as Pennsylvania’s top health official earlier this year.

Despite being equipped to provide up to 6,000 doses a day, the Federal Emergency Management Agency’s clinic at the Convention Center lately has been struggling to get doses in arms. Thursday, health officials had 900 doses of Pfizer vaccine that would have expired if not used that day. Ultimately, those shots didn’t go to waste, said James Garrow, a spokesperson for the Philadelphia Department of Public Health, and as of 2 p.m. 1,000 shots had been administered at the Center City clinic. Earlier in the week, city health officials said they had concerns up to 4,000 might go to waste.

» READ MORE: As expanded eligibility looms, Philadelphia races to vaccinate more than half its senior population

During Levine’s visit, nearly all of the dozens of chairs for people waiting 30 minutes after their shot to ensure they had no serious reactions were empty.

The North Philadelphia clinic at Esperanza, which is administered by FEMA, also has more vaccine than demand for it.

In Philadelphia, vaccinations of seniors have plateaued, with 57% of the city’s 75 and older population receiving at least one shot, and 49% of people 65 to 74 getting a shot. About 80% of seniors nationwide have received at least one shot, officials at the FEMA site said Thursday.

The city also continues to see racial disparities in vaccine administration, with less than a quarter of the city’s Black and Latino populations each having received at least one shot, compared with 41% of whites and 50% of Asian residents.

“I think that we have to now target the harder-to-reach communities in the city, in urban areas, suburban areas, rural areas,” Levine said.

She noted that now 90% of Americans live within five miles of a vaccine provider.

In comments Tuesday, city Health Commissioner Thomas Farley said the Convention Center clinic was administering between 500 and 1,000 shots daily, at best a sixth of its full capacity. The Esperanza clinic, capable of providing at least 1,000 doses per day, had provided a few hundred shots daily.

Levine, though, said FEMA’s work in the city was critical to quickly vaccinating Americans.

“We have made extraordinary progress because of the work being done on the ground,” she said, “just like places like here, like the Center City vaccination center.”

Saturday, the Convention Center site will begin offering single-dose Johnson & Johnson vaccine again after a pause brought on by concerns over the vaccine’s link to a rare but dangerous clotting disorder developing in approximately one out of every million doses administered.

» READ MORE: Philly’s biggest COVID-19 vaccination clinic will get more doses in response to the J&J pause

The city’s fire commissioner and director of the office of emergency management, Adam Thiel, emphasized the focus on smaller neighborhood clinics in the weeks ahead. Those include pop-up clinics at churches and retail stores, he said, and incentives -- as yet unspecified, though they won’t be cash -- to encourage vaccination. All clinics will offer vaccinations without appointments, Thiel said.

“We’re not slowing down,” he said. “We’re going to be doing more pop-ups, more local vaccination clinics.”

About 34% of the city’s population has received at least one shot, according to city data.

The FEMA Center City site is scheduled to continue operating through May 26, with federal authorities providing about two-thirds of the doses there. That volume is not expected to change, Levine said. Despite lower demand, shots allocated to the Philadelphia site won’t be reallocated to countries like India, which is suffering catastrophic COVID-19 surges.

“The situation in India is very severe,” Levine said. The U.S. is sending that country supplies to make vaccine and expects to be able to offer finished doses from the nation’s stockpile of AstraZeneca vaccine.