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, Reuters reports.

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, Reuters reports.

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

Clinical studies show such pre-exposure prophylaxis, or PrEP, can cut the risk of acquiring the virus by more than 90 percent, as long as people take their pills regularly.

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

The United Nations AIDS program 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, Reuters reports.