"I do hope clinicians increase their comfort with being able to provide PrEP to adolescents," said lead author Sybil Hosek, a clinical psychologist and HIV researcher at Cook County Health and Hospitals System's Stroger Hospital in Chicago.
She hopes the new data will be submitted to the U.S. Food and Drug Administration (FDA) and will encourage the agency to approve the pill for use by younger people. The pill is currently approved for HIV prevention in adults.
The drug was first approved by the FDA in 2012 as Truvada, which was marketed by Gilead. Trials found that the drug reduced the risk of HIV infection by over 90 percent.
But little evidence was collected on its use among gay and bisexual adolescent males, who are among those most at risk for HIV infection.
For the study, researchers enrolled 78 gay and bisexual young men, ages 15 to 17, from six U.S. cities. The participants all tested negative for HIV at the start of the study, but were at high risk for an infection.
Participants received a counseling session about HIV risk, plus access to daily doses of PrEP for the next 48 weeks.
Overall, 47 participants completed the study.
Only three adverse events occurred that were possibly related to PrEP, the researchers found.
"I think the safety piece is important," Hosek told Reuters Health. "It was well tolerated. We didn’t see many complaints about side effects. We did not see many adverse events."
The researchers also didn't find an increase in sexually risky behaviors over the study period.
Three young men did become infected with HIV, however. Blood samples suggest they were taking less than two doses of PrEP each week at the time of infection.
The rate of HIV infection in the study was 6.4 cases per 100 people per year, which is about twice as high as the rate seen among men ages 18 to 22 years enrolled in a similar trial, the researchers write in JAMA Pediatrics.
"I shudder to think what the (HIV infection) rate would be if we didn’t offer PrEP," said Hosek.
She said the high rate of HIV infections is likely due to poor adherence. While more than 95 percent of the young men had evidence of the preventive medication in their blood during the first 12 weeks of the study, by week 48 only about 15 percent of participants had detectible levels of the drug.
Low adherence to medications is a common problem with adolescents, said Hosek.
Dr. Renata Arrington-Sanders writes in an editorial accompanying the new study that making PrEP a success among gay and bisexual adolescents will require effort.
"This work suggests that adolescents may require additional visits than what is currently recommended by national guidelines and suggests a need for multiple team members to address structural barriers to accessing PrEP, assist with youths’ interpretation of HIV risk, and support self-efficacy to swallow and adhere to medications," writes Arrington-Sanders, of Johns Hopkins University in Baltimore.
Hosek agreed, calling for doctors to be more connected to their young patients on PrEP.
"Clinicians should not be afraid to see adolescents more frequently, maintain a connection with the adolescents and keep them engaged," she said.