Some 1.2 million Americans are at high risk for HIV and could benefit from taking a daily pill called Truvada. Doctors call the treatment "pre-exposure prophylaxis" or PrEP, say the Centers for Disease Control and Prevention.
Studies show that taking PrEP reduces the risk of contracting HIV and AIDS by 92 percent.
Yet, only about 21,000 people, less than 1 percent of those who could benefit, are taking PrEP.
The Food and Drug Administration approved Truvada in 2012, but one-third of primary care doctors claim they have never heard of PrEP.
"It's one of the best-kept secrets in medicine," said J.D. Davids, managing editor of TheBody.com, an online resource for HIV and AIDS patients.
Many insurance plans cover PrEP, and the uninsured can get Truvada for free through Gilead's patient assistance program.
