NHS England has kicked off what it claims to be the world’s largest single trial assessing the full impact of a scheme that gives patients at high risk of contracting HIV drugs to prevent infection.

Recent evidence indicates that the approach - called pre-exposure prophylaxis (PrEP) - can be highly effective in preventing transmission of the disease as long as the drugs are taken regularly; data from the pilot phase of the PROUD study show that using Gilead's Truvada (emtricitabine and tenofovir disoproxil) in such a way cut the incidence of HIV infection by 86 percent.

In further support of the scheme, an evidence summary by the National Institute for Health and Care Excellence suggests that the provision of PrEP may increase access to other health services such as HIV testing, sexually transmitted infection and hepatitis B screening and support for high-risk sexual behaviour.

From September, PrEP will be provided by the NHS through an initial three-year trial to an estimated 10,000 people, with sexual health clinics in London, Brighton, Manchester, Liverpool and Sheffield expected to be amongst the first to start enrolling people.

Whilst HIV infection rates in England are falling due to increased prevention, diagnosis and treatment programmes, the NHS-England funded intervention will assess the full additional potential of PrEP, by gathering clinical evidence on optimal targeting, uptake and implementation on a large scale.

Clinics will identify eligible participants who consent to the trial, including men, women, transgender people, and individuals who have a partner whose HIV status is not known to be controlled by anti-retroviral treatment.

“This major new intervention should complement and supercharge the wide-ranging and increasingly successful effort to prevent HIV. It’s another milestone in more than three decade’s worth of progress in tackling one of humanity’s major health challenges,” Simon Stevens, chief executive of NHS England.

“This is a pivotal moment in the fight against HIV. PrEP, if targeted properly at those in need and at risk, offers the possibility of transforming the English HIV epidemic,” added Deborah Gold, chief executive at the National AIDS Trust.

“The priority must now be to make sure that the trial is rolled out speedily across the country, and that no-one at risk of HIV is left behind,” stressed Ian Green, Chief Executive of Terrence Higgins Trust. “Now that the PrEP trial drug has been procured, we’re well on the way to protecting over 10,000 people at risk of HIV.”

Last year NHS England argued in court that it doesn't have the legal power to fund a national PrEP service, and that this should instead fall under the remit of local authorities, as they control preventative health. But both the High Court and the Appeal Court disagreed, ruling that the organisation indeed has the ability - but not the obligation - to do so.