LONDON-Scientists are taking the battle to prevent HIV to the next level with large-scale trials set to start using injections to protect vulnerable groups such as gay men and women in Africa for at least two months.

Further down the road, the hope is to produce matchstick-sized implants containing slow-release drugs - similar to existing under-the-skin contraceptive devices - that could offer year-long protection. Companies with drugs involved include GlaxoSmithKline , Gilead Sciences and Merck.

The initiatives build on the success of Gilead’s once-daily pill Truvada, which has proved remarkably effective at stopping HIV infection during sex.

Clinical studies show such pre-exposure prophylaxis, or PrEP, can cut the risk of catching the virus by more than 90 percent, as long as people take their pills regularly. The problem is many do not.

Some women in trials in Africa, for example, said they were reluctant to have HIV tablets in the house for fear of what partners or neighbours would think.

An injection given in a clinic, experts argue, would add privacy and ensure steady drug levels. An implant in the arm might even combine contraception and HIV protection in one go.

“The more options there are the better and I think for some individuals injections will be great,” said Jean-Michel Molina, professor of infectious diseases at Hospital Saint-Louis in Paris.

“Now that we know antiretrovirals have great potential to prevent HIV infections, it is time to really assess other ways to deliver these drugs.”

The need remains acute. Despite treatment advances that have slashed AIDS deaths, around 1.9 million people still catch HIV each year - a number that hasn’t budged since 2010. New infections among gay men are actually increasing.

The United Nations AIDS programme warned last week that the problem now threatened progress in ending the global epidemic, while the World Health Organization has recommended PrEP for all groups at substantial risk of HIV infection.

GlaxoSmithKline’s majority-owned ViiV Healthcare unit, working with US government agencies and the Bill & Melinda Gates Foundation, hopes to add the first injectable PrEP.

It plans to start a four-year trial as soon as next month testing its experimental drug cabotegravir in gay men in the Americas and Thailand, with a second trial next year assessing the medicine in African women. Two separate studies evaluating cabotegravir in combination with another drug for HIV treatment were launched this month.

“The holy grail is a vaccine, but we don’t have a vaccine yet,” said Myron Cohen of the University of North Carolina at Chapel Hill, who is involved in the ViiV prevention study programme and believes new options can help rein in HIV.

He is also working on another prevention trial giving people antibodies via an intravenous drip. Gilead, meanwhile, is running a late-stage study assessing its next-generation HIV drug Descovy as an alternative oral PrEP, since it has milder side effects than Truvada.

In the long run, Cohen and other HIV experts are especially excited by slow-release drug implants. Implants have yet to prove themselves in human trials, although an experiment in beagles last year with a Gilead drug produced promising results. Products from GSK and Merck are also seen as implant options. Meanwhile, One in seven people with HIV in the Europe Union region is unaware they have the virus, seriously hampering efforts to meet a global 2030 deadline for eradicating the AIDS epidemic, a senior health expert said on Tuesday.

The average estimated time between infection and diagnosis is four years with nearly half of people not being diagnosed until the late stages of the disease, according to a report published ahead of World AIDS Day on Dec 1.

Around 810,000 people are believed to be living with HIV in the EU’s 28 member countries plus Norway, Iceland and Liechtenstein, the report by the European Centre for Disease Prevention and Control (ECDC) shows.

But the ECDC estimates 122,000 are unaware they have the virus.

Andrea Ammon, acting director of the ECDC, said it was worrying that the number of new infections every year had remained constant for a decade and called for testing services to be ramped up. “The findings are definitely of concern. They tell us that we still have a lot to do despite all the HIV prevention efforts,” Ammon told the Thomson Reuters Foundation.

Almost 30,000 newly diagnosed HIV infections were reported last year in the region, according to the joint report with World Health Organization (WHO).