A new drug described as “the closest we have ever been to an HIV vaccine” could cost $40 (£31) a year for every patient, a thousand times less than its current price, new research suggests.

Lenacapavir , sold as Sunlenca by US pharmaceutical giant Gilead, currently costs $42,250 for the first year. The company is being urged to make it available at a thousand times less than that price worldwide.

UNAids said it could “herald a breakthrough for HIV prevention” if the drug was available “rapidly and affordably”.

Given by injection every six months, lenacapavir can prevent infection and suppress HIV in people who are already infected.

In a trial, the drug offered 100% protection to more than 5,000 women in South Africa and Uganda, according to results announced by Gilead last month.

Lenacapavir is currently licensed for treatment, not prevention.

In a study presented at the 25th international Aids conference in Munich on Tuesday, experts calculated that the minimum price for mass production of a generic version, based on the costs of lenacapavir’s ingredients and manufacturing, and allowing for 30% profit, was $40 a year , assuming 10 million people used it annually. In the long-term, 60 million people would probably need to take the drug preventatively to lower HIV levels significantly, they said.

Dr Andrew Hill, of Liverpool University, who led the research, said: “You’ve got an injection somebody could have every six months and not get HIV. That’s as close as we’ve ever been to an HIV vaccine.”

Most HIV prevention presently relies on daily pills and barrier measures, such as condoms.

Campaigners want Gilead to allow generic licensing through the UN-backed Medicines Patent Pool in all low- and middle-income countries (LMICs), which account for 95% of HIV infections. Similar mechanisms have been in place in the HIV treatment market for decades, where wealthy countries pay higher prices than poorer ones.

If that did not happen, Hill said, countries should consider issuing compulsory licences allowing generic manufacture in the face of a public health emergency.

Gilead said it was “too early” to price lenacapavir for prevention, as it was awaiting clinical trial data and potential regulatory filings, but promised “a strategy to enable broad, sustainable access globally”.

This would include both “Gilead supply in the countries where the need is greatest until voluntary licensing partners are able to supply high-quality, low-cost versions of lenacapavir” and a voluntary licensing programme for “high-incidence, resource-limited countries”. Gilead said choosing those countries was ongoing.

But campaigners said it was vital that all LMICs, including “upper middle-income” nations such as Brazil, had access to low-cost generic forms of the drug.

Similar selections in the past had excluded countries where the HIV epidemic was growing fastest, they said.

Trials in LMICs made the case for universal access even stronger, Hill said, pointing to the Helsinki Declaration on medical ethics, which said that trials should only be performed in populations who stood to benefit from the results.

Joyce Ouma, senior programmes officer at Y+ Global, a network of young people living with HIV, said a twice-yearly injectable would be “transformative for young people like me living with or at risk of HIV”.

Ouma said: “It’s not an exaggeration to say that meeting the 2030 goal of ending new HIV transmissions hinges on Gilead ensuring people in the global south have fair access to lenacapavir.”

Winnie Byanyima, executive director of UNAids, said treatment could be “life-saving” by providing a more discreet option than daily tablets for people who faced stigma because of their HIV status or sexuality.