CHICAGO (CBS) — A big vaccination milestone in Chicago, as half of all those eligible to get the COVID-19 vaccine have had at least one dose, and that percentage could begin to soar.

City-run sites, including the United Center, will start accepting walk-ins on Friday, and CBS 2’s Mugo Odigwe tells you what you need to know.

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Chicago Department of Public Health Commissioner Dr. Allison Arwady said the city is finally receiving an ample supply of vaccines, after months of not being able to meet demand for shots.

“Our supply has just not been up to our demand month after month after month, and I know how frustrating that has been for many people, but as of now, we have enough vaccine,” Arwady said on Thrusday. “If you want a vaccine in Chicago, you can absolutely get one. You can get one today. No excuses.”

Vaccine appointments are open through May 6 at the United Center, but if you just happen to be in area, you can now stop by and still get a shot without an appointment.

“Like God sent me a message, ‘Go get the shot today,’” said Roman Ortega, one of the first people to walk in for a vaccine at the United Center on Friday.

Ortega said he’s tried and failed to get a vaccine appointment before, so the moment he learned he could just walk in at the United Center mass vaccination site and get a shot, he wasted no time getting there.

“Actually, I saw it this morning on the news,” he said. “It worked out. I was off today, too, so it worked out.”

Perfect and accommodating; that’s how he described having the option to walk-in for a vaccine shot.

Others who also showed up for the walk-in option would agree.

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“It’s decent. I liked it. It’s great. Like you said, you can come on through here and walk in,” Jimmie Collins said.

“Cut the red tape. You just walk up and then, hopefully, it looks like we’re going to be waiting in line a while though, but I think it’s important,” Phil Faso said.

Even though the walk-in line is long, Ortega said, “I don’t mind.”

“I’m here. I’m going to stay. I’m going to get the shot,” he said.

Since the city’s vaccination clinics use the Pfizer vaccine, the only vaccine approved for 16- and 17-year-olds, the shots are available to anyone age 16 and up, but anyone under 18 must come with a parent or guardian.

While walk-ins are now allowed at city-run vaccination sites in Chicago, officials are still encouraging people to schedule an appointment to avoid long lines, and guarantee a shot will be available when they show up.

“That’s going to be the best way. Go on zocdoc, or call the call center. If you make an appointment, you won’t need to be standing in long lines, you’ll know for sure you have an appointment,” Arwady said Thursday. “But we know that a lot of people are still having challenges getting appointments, and we know there’s digital divides, and we know there’s people who maybe, spur of the moment, might say, ‘Let’s get a vaccine.’”

Appointments at city-run vaccination sites are available online at zocdoc.com/vaccine or by calling 312-746-4835.

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Meantime, earlier this week, Cook County Health started accepting walk-ins at its Matteson, Summit and Tinley Park vaccination sites. You’ll need a photo ID to register on-site. Their pilot program will continue through Saturday.