EXPERTS hailed twice-yearly shots used to treat Aids that were 100 per cent effective in preventing new infections in women, according to study results published today.

There were no infections in the young women and girls that got the shots in a study of about 5,000 in South Africa and Uganda, researchers reported. 

In a group given daily prevention pills, roughly 2 per cent ended up catching HIV from infected sex partners.

Salim Abdool Karim, the director of an Aids research centre in Durban, South Africa, which was not part of the research, said: “To see this level of protection is stunning.”

The shots made by United States drugmaker Gilead and sold as Sunlenca are approved in the US, Canada, Europe and elsewhere, but only as a treatment for HIV. 

The company said that it is waiting for results of testing in men before seeking permission to use it to protect against infection.

The results in women were published on Wednesday in the New England Journal of Medicine and discussed at an Aids conference in Munich. 

Gilead paid for the study and some of the researchers are company employees. Because of the surprisingly encouraging results, the study was stopped early and all participants were offered the shots, also known as lenacapavir.

The prospect of a twice-a-year shot is “quite revolutionary news” for our patients, said Thandeka Nkosi, who helped run the Gilead research at the Desmond Tutu Health Foundation in Masiphumelele, South Africa. 

“It gives participants a choice and it just eliminates the whole stigma around taking pills” to prevent HIV.

Experts working to stop the spread of Aids are excited about the Sunlenca shots but are concerned Gilead hasn’t yet agreed on an affordable price for those who need them the most. 

The company said it would pursue a “voluntary licensing programme.”

Winnie Byanyima, executive director of the Geneva-based UN Aids agency, said: “Gilead has a tool that could change the trajectory of the HIV epidemic.”

She said that her organisation urged Gilead to share Sunlenca’s patent with a UN-backed programme that negotiates broad contracts allowing generic drugmakers to make cheap versions of drugs for poorer countries worldwide. 

As an HIV treatment, the drug costs more than $40,000 (£31,000) a year in the US, although what individuals pay varies.

Globally, HIV infects about 1.3 million people every year and kills more than 600,000, mainly in Africa. While significant progress has been made in Africa, HIV infections are rising in eastern Europe, Latin America and the Middle East.