From morning through midday Wednesday, the line stretched down 12th Street, a parade of humanity that included seniors, restaurant workers, caregivers, and folks with health problems, all there for Philadelphia’s largest mass vaccination site yet.

“I been keeping up with it on the news and everybody said it’s safe,” said Clarence Goldsby, 55, who was joining his elderly mother for their first COVID-19 vaccine doses. She needs his help, but before getting vaccinated he feared every bus trip to see her carried the risk he could bring COVID-19 into her home.

Philadelphia Department of Public Health officials anticipated about 6,000 people would receive shots at the Convention Center on Wednesday, the first day of full operation for the Federal Emergency Management Agency-operated site. Philadelphia has reported about 50,000 people a week vaccinated citywide recently. The FEMA site alone, operating every day for at least the next eight weeks, is expected to nearly double that weekly figure.

» READ MORE: Pa. counties are blaming ‘cumbersome’ state-provided software for vaccine registration problems

The site is one of the first signs of a more robust vaccine rollout. Anticipating an increase in vaccine supplies, Pennsylvania is enlisting the state National Guard to help set up regional inoculation sites. Gov. Tom Wolf on Wednesday signed a bill that authorizes the Guard to work with the state Health Department in planning and operating sites.

At the Philadelphia site, the line was long, but moved briskly.

FEMA staff in yellow vests and a Navy corpsman walked the line in the morning, asking those waiting if they had any flu symptoms, felt well enough to get a shot, and if they had a required appointment.

”I’m really excited about getting a shot,” said Rosy Kong-Quee as she waited in line.

The North Philadelphia woman has hypertension, she said, and she registered for an appointment at the site two weeks ago.

Lindsey Shawver, 27, wore a mask decorated to look like the carpet from the haunted hotel in the horror movie The Shining as she waited in line with a friend.

Shawver has kept working throughout the pandemic as a restaurant server, she said, but otherwise barely leaves home.

”Socially I’ve been home for the past year,” she said.

» READ MORE: COVID-19 vaccine allocation creates ‘vaccine deserts’ in parts of Philly

When people in line reached the Convention Center, they walked through three rounds of identification checks before their appointments, an apparent safeguard to keep out ineligible line-jumpers.

“Thank you for getting vaccinated with us,” a staffer said, leading people past the checkpoint in one of the main halls — a room the size of a city block.

There, dozens of Marines sat at long tables, with a vaccine recipient waiting on either end for their shot.

Afterward, recipients waited in folding chairs spaced six-feet apart for 15 minutes to ensure they had no serious side effects such as a rare allergic reaction requiring immediate treatment. They tapped on their phones or chatted with family members before lining up to schedule their second shot.

» READ MORE: For Philly hospitals, phone calls more effective than digital platforms at registering seniors for COVID-19 vaccines

The smooth operation contrasted with the complication of hundreds of people not yet eligible for vaccination making appointments at the site during a soft opening Monday and Tuesday intended for a select group of essential workers. An online link intended only for those workers was shared, city officials said, and the registration software, PrepMod, had no ability to prevent someone other than the intended recipient from using it to sign up for an appointment.

The city ultimately had to cull more than 100 appointments from the schedule on Monday and Tuesday. By Wednesday, though, a different link was being used to make appointments, and the cascade of people trying to get doses had shrunk.

» READ MORE: Philly’s first federal COVID-19 mass vaccination site already is having to fend off people who aren’t eligible

“This was much less of an issue on Tuesday and beyond,” said Matthew Rankin, a Department of Public Health spokesperson, though the city is still filtering through appointments to try to identify ineligible people.

The city has yet to resolve its inability to restrict access to registration links, though a fix is promised soon, Rankin said. Anyone who is seeking a vaccine dose should submit information to the vaccine interest database, at covid-vaccine-interest.phila.gov. If they’re eligible and there are doses available, they should later receive an invitation to make an appointment.

PrepMod has been causing problems nationally as well as in Pennsylvania. The software has saved workers from having to do tedious data entry work, but along with the private invitation link problem, the system has been reported to overbook appointments, send people incorrect scheduling information, and allow those not currently eligible for vaccination to make appointments.

All those problems weren’t apparent when the city agreed to use PrepMod in the fall, Rankin said.

“PrepMod had been recommended by the CDC and was chosen based on that recommendation.” he said. “The ‘well-documented’ issues with this software are only now being documented and were not available when PrepMod was chosen.”

Tiffany Tate, executive director of the Maryland Partnership for Prevention, the nonprofit responsible for the software, did not return a call for comment.

Staff writer Anthony Wood contributed to this article.