The United States will relax a decades-long ban on blood donations from gay men. The new policy will allow men who have sex with men to donate, but only if they abstain from sex for one year. The change could take effect as early as mid-2015.

The Food and Drug Administration has long banned donations from gay men

The Food and Drug Administration currently prohibits blood donations from men who have had sex with other men even once since 1977 — the year the AIDS epidemic took off in the US.

According to the FDA, this policy is based on the group's heightened risk for HIV, hepatitis B, and other blood-borne infections.

Other groups that are seen as high-risk carriers for blood-borne infections are also barred from giving blood. This includes intravenous-drug abusers, sex workers, HIV-positive people, and those who received transplants of animal tissue or organs since there's still uncertainty about "risks of transmitting unknown or emerging pathogens harbored by the animal donors."

The new policy will allow donations from some gay men

On November 13, a panel that advises Health and Human Services recommended lifting the 31-year ban on blood donations from gay and bi men. At that meeting, secretary's Advisory Committee on Blood and Tissue Safety and Availability met to review the latest science, and voted 16-2 to replace the ban with a one-year deferral period.

This was a big deal because past groups of HHS advisers voted to keep the lifetime ban in place. The latest vote reflects the fact that they think the evidence overwhelmingly suggests it's safe to change the policy.

On December 23, the Food and Drug Administration (part of Health and Human Services) announced it would follow the Advisory Committee's recommendations.

The policy still excludes gay men in monogamous relationships

The new FDA policy will only allow donations from gay men who have gone at least "one year since the last sexual contact." This will still exclude men in monogamous relationships, which experts say doesn't serve much of a public health purpose.

"There are irrational aspects of the policy," said Sean Cahill, director of health policy research at the Fenway Institute. "If you are a heterosexual man who admits to having unprotected sex with a sex worker or prostitute, you can wait one year and donate blood. But a gay man who has been in a monogamous relationship and who tests negative for HIV still can't."

Glenn Cohen, a Harvard Law professor who wrote about the blood donor rule in JAMA: the Journal of the American Medical Association, sees a one-year deferral as an interim step, but thinks it's not any more evidence-based than the current lifetime ban.

"There's no medical reason to think that a one-year deferral makes a difference as opposed to a month-long deferral when the virus would show up in blood," he explained.

Cohen says these long deferrals on gay and bi men are a hangover from the early days of HIV, when the disease was known as GRID, or "gay-related immune deficiency."

But maybe an evidence-based blood policy is too much to ask for when fears about gay men's blood still abound. "It's not just about the safety of the blood supply," Cohen said, "it's about the perceived safety of the blood supply."