LONDON (AP) — Britain's High Court has ruled that the state-funded health service is responsible for paying for an HIV-prevention drug that has been called a "game changer" in the fight against AIDS.

The National AIDS Trust charity argued that health authorities have an ethical duty to fund the pre-exposure prophylaxis drug (PrEP), which reduces the risk of becoming infected with HIV.

The health service argued that it was not responsible for preventing sexually transmitted diseases, because public health measures fall to local government.

Judge Nicholas Green ruled Tuesday that the health service "erred in deciding that it has no power or duty" to commission the treatment.

Dr. Michael Brady, medical director of AIDS charity the Terrence would "significantly increase the momentum in our fight against the virus."