(CNN) The US Food and Drug Administration issued new blood donation eligibility guidance Thursday as US blood supplies decrease amid the coronavirus pandemic. The changes are to be implemented immediately and are expected to remain in place after the pandemic ends.

The FDA has guidelines in place to reduce the risk of transmitting HIV through blood, and is shortening its recommended blood donation deferral period for some groups: For male donors who have had sex with another man, female donors who would have been deferred for having sex with a man who had sex with another man and for those who recently got tattoos or piercings, the recommended blood donation deferral period changes from 12 months to three months.

US Surgeon General Jerome Adams said in a media briefing following the release of the new guidelines that HIV-positive people are still barred from giving blood.

But those taking taking a pre-exposure prophylaxis, or PrEP, to prevent HIV infection can still donate if they're not using the medication to treat HIV infection, said Dr. Peter Marks, the FDA's director of the Center for Biologics and Evaluation Research, who participated in the briefing.

Whether they need to discontinue the use of the medication and for how long is up to the donation center, he said.

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