Leon Richardson is 18 years old and tall, charismatic and thoughtful about his sexual health.
He understands that as a young, gay black man, he is in the demographic with the highest rate of HIV infections in the country. But when Richardson learned that he could be part of an HIV prevention pill research study for young people, he was skeptical.
"I was scared. I had to really think about it, 'What is this drug going to do to me?' " he says.