Scientists have found that an injection given every two months is 89% more effective in preventing HIV infection than daily anti-retroviral pills.
More than 3,200 women from east and southern Africa who were at a higher risk of contracting HIV took part in the trial.
The United Nations has called for investment in the injectable anti-retroviral – known as cabotegravir – hailing it as a real game-changer.
Scientists say those at risk of infection are more likely to adhere to having an injection every eight weeks than taking daily pills, thus further reducing the spread of the disease.
Anti-retrovirals, which are used to treat HIV, also help prevent infection.