Every night at 8 p.m., 18-year-old Catherine Msimango takes a pill.
It's the same pill that people with HIV take to fight the virus. Only she doesn't have HIV.
Msimango says the pill gives her power against the virus. She can take it even without her boyfriend knowing.
"It's all about my safety because I don't know what he does when I'm not around," she says. "If he doesn't want to use protection [a condom], I know that I'm safe from the pill."