CHICAGO (AP) — Mayor Lori Lightfoot and Illinois Gov. J.B. Pritzker on Monday said limiting the mass vaccination site at Chicago's United Center to city residents is due to the federal government wanting to make sure people most in need are being vaccinated.

According to officials, more than 40,000 people 65 and older booked appointments at the United Center since registration began Thursday. However, fewer than 40% of them were Chicago residents.

Lightfoot said Monday the disparity prompted discussions about ensuring the appointments were open to more Black and Latino city residents.

Pritzker said a result of weekend negotiations with the Federal Emergency Management Agency over the United Center vaccination policy, the state is securing additional vaccine doses on top of its usual allotment. Those does will be used at federally run mobile vaccination sites outside Chicago.

“FEMA came late in the game here and decided they wanted to change things,” Pritzker said. “And it took a little while for the city of Chicago, FEMA and the state to come to some understanding of what the best way to move forward was.”

A FEMA spokesman said data from the Centers for Disease Control social vulnerability index prompted establishment of community vaccination centers where they will do the most good for the most vulnerable populations. The spokesman said it was agreed by local, state and federal officials the changes at the United Center were necessary to ensure that goal was met.

Those who made their appointments prior to Sunday’s eligibility change can keep their appointments even if they live outside the city, Pritzker said. A second website is being established so that suburban Cook County residents can eventually sign up for vaccine appointments at the United Center.

Chicago public health Commissioner Dr. Allison Arwady says the United Center site may eventually be open to all Illinois residents. The site is scheduled to open Tuesday to a limited number of people before a full opening on Wednesday.

Illinois public health officials officials on Monday reported 1,182 new confirmed and probable cases of COVID-19 and five additional fatalities. The number of known infections in Illinois since the pandemic began is 1,199,517, with 20,767 deaths.