The U.S. has approved the first drug shown to reduce the risk of HIV infection, a milestone in the 30-year battle against the virus that causes Aids, Belfast Telegraph said.

The Food and Drug Administration approved Gilead Sciences' pill Truvada as a preventive measure for people who are at high risk of acquiring HIV, such as those who have sex with HIV-infected partners.

Gilead Sciences has marketed Truvada since 2004 as a treatment for people who are infected with the virus, but company studies have shown the drug can prevent people from contracting HIV when used as a precautionary measure.

A three-year study found that daily doses cut the risk of infection in healthy gay and bisexual men by 42%, when accompanied by condoms and counselling.