CHICAGO (CBS) — Mayor Lori Lightfoot said on Twitter Sunday that more than 40,000 people over 65 have signed up for COVID-19 vaccines at the United Center, but fewer than 40 percent of the appointments were actually made by Chicago residents.

Health officials said appointments made by people who live outside the city will still be honored. But effective immediately, appointments through Zocdoc will be limited only to residents of the city of Chicago.

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For those in suburban Cook County, appointments at the United Center will be made available in the coming days. Officials will announce details of that registration process later this week.

Residents outside of Cook County will no longer be eligible for appointments at the United Center site.

Meanwhile, the Chicago Department of Public Health said all vaccine appointments at the United Center site through Zocdoc are now booked, with additional appointments opening up later this week.

“Equity has always been the guiding light for our vaccine rollout,” Mayor Lightfoot said on Twitter. “And to ensure that remains our priority, we’ve partnered with the State of Illinois and Cook County to have Chicago residents who are 18+ with underlying conditions become eligible to make vaccination appointments.”

The city advised that slots are set aside for the city’s vaccine call center, which will open Monday at 8 a.m. so people without have internet access can still make appointments. The Public Health Department said a limited number of vaccines will be administered on Tuesday, and the United Center site will open fully on Wednesday.

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Beginning at 4 p.m. Sunday, the appointment pool at the United Center site extended to those 16 and older with medical conditions.

On Saturday, CBS 2’s Steven Graves reported some people trying to sign up for vaccine appointments at the United Center ran into glitches.

Both Friday and Saturday, people were noticing emails with cancellations or rescheduling. That came after they were one of the tens of thousands who booked slots last Thursday on the Zocdoc site. The emails called the cancellations “an unfortunate technical issue.”

Messages also went out from the City of Chicago about a rescheduled slot, and then a follow-up that says there was a mistake.

It is unclear what is causing the website glitches. The group Vaccine Angels helpers think efforts to sign up multiple people at once might be the issue.

Officials are encouraging seniors to call the UC hotline which now has expanded its capacity.

The number for that hotline is (312) 746-4835.

The Public Health Department said those who live in Cook County, but not Chicago, should go to vaccine.cookcountyil.gov. Those who live outside of Chicago and Cook County should go to coronavirus.illinois.gov.

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The city also said questions about website functionality issues should go to Zocdoc.

CBS 2 Chicago Staff