Dapivirine vaginal ring and oral pre-exposure prophylaxis (PrEP) are effective HIV prevention measures in adolescent girls, according to two studies presented at the International AIDS Society Conference on HIV Pathogenesis and Treatment in Paris.

These solutions could be critical in lowering the rate of HIV and AIDS in girls between the ages of 15 and 25 years, a population that has proven to be particularly vulnerable to HIV infection, researchers say.

Females aged 15-24 years made up 20% of new HIV infections globally in 2015, even though they represented only 11% of the adult population, according to the National Institutes of Health (NIH).

“Adolescents and young people represent a growing share of people living with HIV worldwide,” Anthony S. Fauci, MD, director of the National Institute of Allergy and Infectious Diseases (NIAID) said in a statement released by the NIH. “Science has demonstrated that the HIV prevention needs of adolescents may be different than those of adults, which is why these new study findings are so important.”

In a phase II, double-blind, placebo-controlled trial, researchers administered a 25-mg dapivirine vaginal ring to 73 patients, with a placebo group of 23 patients, gathered from six sites across the United States once every 4 weeks over a period of 24 weeks.

Patients’ ages ranged from 15 to 17 years of age and a majority were African American, with a median of three sexual partners over the course of their lifetimes.

After the 24-week period, dapivirine residual drug levels indicated a 95% adherence rate, with a reported 42% of patients in the test group reporting never having removed the vaginal ring.

Among the patients given the ring, 63% reported never feeling the ring during intercourse, while 73% of those who said they did feel the ring reported not being bothered by it.

Overall, 93% of the study population reported not being bothered by the solution, which investigators interpreted as a positive sign for the dapivirine ring as an effective HIV prevention tool.

“We are encouraged by these results of the dapivirine ring in 15- to 17-year-old girls,” Sharon Hillier, PhD, of the NIH-funded Microbicide Trials Network (MTN), said in the NIH statement. “The study has demonstrated that the ring is safe in U.S. teens, and now we need data on the safety and acceptability of the ring in African adolescent girls. The REACH study, scheduled to launch later this year, will generate [these] data.”

In a second study presented at the conference, investigators tested the safety and acceptability of daily oral Truvada (emtricitabine/tenofovir) as a PrEP solution in 148 HIV-free adolescents aged 15-19 years from two study sites in South Africa over a span of 12 months. Truvada has not yet been approved by any national regulatory body for use as oral PrEP in adolescents.

Patients were majority female (99 girls/49 boys), with 74% of the population reporting having used a condom during their last sexual encounter.

At the start of the trial, sexually transmitted infections were present in 40% of participants, a level that remained constant throughout the study.

A total of 16 (11%) participants reported grade 2 adverse effects, including headaches, nausea, abdominal pain, and skin rashes, with another 2 patients reporting weight loss during the trial, according to Katherine Gill, MBBS, of the Desmond Tutu HIV Foundation, Cape Town, South Africa.

One instance of HIV infection was reported, although the patient in question dropped out of the program 24 weeks before diagnosis.

Overall, investigators found the Truvada PrEP program to be reasonably well tolerated, with plasma tenofovir levels detectable in 57% of participants after 12 weeks, 38% after 24 weeks and 38% at the end of the study, according to Dr. Gill and her colleagues.

Both studies were funded by NIH grants. Investigators of both studies reported no relevant financial conflicts.

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