A cyberattack Wednesday on one of America’s largest health care technology companies has left U.S. military pharmacies worldwide unable to fill prescriptions, the Defense Health Agency said Thursday.

“A reported cyberattack on the nation’s largest commercial prescription processor, Change Healthcare, has affected military clinics and hospitals worldwide,” DHA said in a statement.

Change Healthcare disconnected its systems on Wednesday to protect patient information, according to the agency.

“This is impacting all military pharmacies worldwide and some retail pharmacies nationally,” DHA said.

News reports indicated large retail chains in the U.S. like CVS and Walgreens and local pharmacies across the country were experiencing delays or interruptions in their ability to fill customers’ prescriptions Wednesday.

Change Healthcare is part of Optum, a health technology company acquired by UnitedHealth Group in 2022. Change Healthcare processes patient payments for many health care entities, including pharmacies, in the United States.

The firm said in a website update Thursday it had disconnected its system “in the interest of protecting our partners and patients” and to “prevent further impact.”

“At this time, we believe the issue is specific to Change Healthcare and all other systems across UnitedHealth Group are operational,” the update states. “The disruption is expected to last at least through the day.”

DHA said that military clinics and hospitals will provide outpatient prescriptions through a manual procedure until the problem is resolved.

“Military pharmacies will give priority to urgent prescriptions followed by routine prescriptions,” DHA said in its statement. “Each military hospital and clinic will continue to offer pharmacy operations based on their local manning and resources.”

Pharmacies at U.S. military bases worldwide have issued advisories asking patients to forego filling prescriptions until the system is back online.

The 374th Medical Group at Yokota Air Base in Tokyo told its population Thursday that it was temporarily unable to fill prescriptions through the recently installed MHIS Genesis online medical records system. The base pharmacy is handing out fulfilled requests but asked patients to wait on new requests or see their physicians, according to a post on the official Facebook page.

Naval Health Clinic Hawaii said in a Facebook post Thursday its pharmacies at Joint Base Pearl Harbor-Hickam and Marine Corps Base Hawaii had “implemented down-time procedures and are able to fill needed prescriptions,” but that patients should expect longer wait times.

“If you have remaining medication at home, we ask that you please consider waiting until the issue has been resolved,” the post states.

Scott Air Force Base Clinic in Illinois said in a Facebook post Wednesday that due to a “DoD-wide outage” its pharmacy was “facing heavy delays with both activation and refill for prescriptions.”

“At this time, we are unable to process any new activations,” the post states. “You can still call in a refill, however it won’t be processed until the system comes back up.”

The 72nd Medical Group at Tinker Air Force Base in Oklahoma said in a Facebook post Thursday that it also could not fill prescriptions.

“Some TRICARE network pharmacies may also be impacted by the outage,” the post states.

Bassett Army Community Hospital in Fort Wainwright, Alaska, said in a Facebook post Thursday that it was unable to fill prescription and encouraged patients to wait if possible.

“Please note, filling prescriptions at a non-[military treatment facility] pharmacy will incur a copay/charge in most cases,” the post states.

The American Hospital Association said in an advisory Thursday that it had been communicating with the FBI, Department of Health and Human Services and the Cybersecurity and Infrastructure Security Agency regarding the cyberattack and outage.

The association recommended that organizations using Change Healthcare’s services should prepare contingency plans in case the outage continues for an extended period.