Truvada is one of the ARV drugs that are currently used as a daily pre-exposure prophylaxis, or PrEP. Image: 123RF/Alexander Raths Women who are at risk of HIV infection and are using HIV pre-exposure prophylaxis (PrEP) on a daily basis might in the near future have to use only one pill a month, if a trial conducted in SA and other parts of the world is successful. This week the efficacy study, which is led by the University of Washington, received a $122m grant from the Bill & Melinda Gates Foundation to test the effectiveness of a once-a-month oral pill to prevent HIV.