CHICAGO (AP) — Changes at the U.S. Postal Service resulted in the delayed delivery in July of 5,000 prescriptions filled by Cook County Health’s mail-order pharmacy, an official said Monday.

Cook County Health Chief Medical Officer Dr. Claudia Fegan said the Chicago pharmacy normally fills more than 20,000 prescriptions monthly. She said 23% of those prescriptions were delayed, up from less than 1% in March. She said there were also delays in April and May, reaching 18% in June.

“This is yet another example of the impact that policy changes have on our vulnerable populations,” Fegan said. “They deserve to be able to receive their medication and not have to worry about how they’ll get to the pharmacy during a pandemic to get their medications.”

The COVID-19 pandemic has pushed the Postal Service into a central role in the 2020 elections, with tens of millions of people expected to vote by mail rather than in-person.

Postmaster General Louis DeJoy appeared Monday before a U.S. House committee hearing on the operational changes that have reportedly resulted in delivery delays nationwide. Democrats said the changes under DeJoy’s watch are causing widespread delays, but Republicans dismissed the worries as unfounded and part of a Democratic “conspiracy” against Trump.

DeJoy has downplayed delivery delays and said the agency is fully capable of processing this year’s mail-in ballots.

Representatives of Sinai Health System, University of Chicago Medicine and Amita Health said they haven’t recently seen delays in mail-order prescription delivery. Some health systems’ pharmacies use the postal service, while others use FedEx or UPS.

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