Additional Study Information: Pre-exposure prophylaxis, or PrEP, is the term used for medications that reduce the risk of getting HIV. There are approved medications that can be taken daily to prevent HIV infection. We are studying a PrEP medication that is a pill that can be taken once a month. It is being compared to an approved PrEP pill that is taken once daily. All women who take part in this study will be randomly placed into one of two study treatment groups. 1) Group 1: Take the monthly study medication plus a placebo of the approved daily medication. 2) Group 2: Take the approved daily medication plus a placebo of the monthly study medication. The placebos look like the study medication or the approved medication, but have no active ingredients. Neither you nor the study staff will know which treatment group you are in. All women who take part in this study will have their health closely monitored by the study team. Tests that take place include physical exams, blood and urine tests, STI (sexually transmitted infections) screening and HIV testing. Participants will be in this study for an average of about 1.5 years but possibly up to about 3 years, will visit the study site monthly and speak to study staff by phone a few times. Participants will receive compensation for their time and travel to the site.