Chicago's United Center mass vaccination site limited appointments to Chicago residents Sunday after most of the initial slots went to people who don't live in the city.
"Equity has always been the guiding light for our vaccine rollout," Lightfoot added.
The United Center is one of 18 community vaccination centers that are part of a federal plan to bring the vaccine to hard-hit, high-risk communities.
"Vaccines for these centers are provided to the states above and beyond the regular allocations," according to FEMA.
To determine locations for those centers, the Federal Emergency Management System (FEMA) and the Centers for Disease Control and Prevention (CDC) worked with state and local partners. They used the CDC's social vulnerability index, which uses census data to identify communities that need support before, during and after disasters.
When it reaches full capacity, the United Center site will be capable of administering 6,000 vaccines per day.
In Illinois, 8.8% of the population has received two doses of the vaccine, compared to 9.2% of the population nationwide, according to the CDC.