Pills costing 15p are 'major breakthrough' in fighting Aids

Until a year ago the fight against Aids was focused on behaviour, such as using condoms and having fewer partners

A once-a-day pill that can prevent HIV was hailed by researchers yesterday as two studies showed it could provide up to 73 per cent protection for heterosexuals against the disease that has claimed almost 30 million lives.

The studies involved more than 5,000 couples in three African countries – Kenya, Uganda and Botswana – where one partner was HIV-negative and one HIV-positive. The researchers found that when the uninfected partner took the daily pill their chances of contracting the disease were reduced by between 62 per cent and 73 per cent compared with those who took a placebo.

Margaret Chan, director general of the World Health Organisation, said: "These studies could have enormous impact in preventing heterosexual transmission."

The findings are the latest to suggest the Aids pandemic, which has raged for three decades, may be contained by chemoprevention – the development of drugs and vaccines which curb its spread. The drugs, Truvada and Viread, are available in generic versions and cost as little as 15 pence each.

Michel Sidibé, executive director of UNAIDS, the Joint United Nations Programme on HIV/Aids, said: "This is a major scientific breakthrough. These studies could help us to reach the tipping point in the HIV epidemic."

Until a year ago, the prevention of Aids focused on changing behaviour, such as promoting condom use, reducing the number of sexual partners and abstinence. But in the last 12 months, drug treatment with Truvada has been shown to reduce rates of infection in gay men and use of a vaginal gel has reduced infection in heterosexual women. An Aids vaccine was partially effective in a trial in Thailand and male circumcision was shown years ago to provide up to 60 per cent protection against female-to-male infection.

But budget constraints will limit the use of prevention drugs. Just 6.6 million of the more than 15 million HIV-positive people estimated to need drug treatment are currently getting it, according to UNAIDS. And financing for HIV/Aids fell for the first time for the world's poorest countries in 2010.

UN member states agreed last month to scale up treatment to reach 15 million people by 2015, but providing drugs to protect those not infected will need a further scale up.

Drug treatment would not be appropriate for everyone at risk because of the side-effects and cost. But scientists say that preventive treatment for some groups, such as sex workers, could be cost-effective.

Anthony Fauci, director of the US National Institute of Allergy and Infectious Diseases, said: "As we get more scientific data, the ability to contain the epidemic by multiple weapons gets better and better. Major investment now will save even greater expenditure in the future.

"For the first time in the history of HIV/Aids, controlling and ending the pandemic are feasible."