A vaginal ring to prevent HIV infection is popular with teenage girls, US scientists say.
Women and girls aged 15-24 account for a fifth of all new HIV infections globally. Nearly 1,000 are infected every day in sub-Saharan Africa.
Infused with microbicides, the ring, which sits on the cervix, has been shown to cut infections by 56%.
Experts say it frees women from relying on men to wear condoms and allows them to protect themselves confidentially.
Dr Anthony Fauci, the director of the US National Institute of Allergy and Infectious Diseases, told the BBC: "If you can give women the opportunity to protect themselves in a way that is completely confidential - that's a long and big step to helping them.
"In societies where women are, unfortunately but true, somewhat second-class citizens, that makes women extremely vulnerable to getting infected with HIV."
The flexible ring, similar in size to the contraceptive diaphragm, releases an antiretroviral drug called dapivirine for a month.
But scientists were unsure it would work in teenagers, who can be notoriously difficult when it comes to health advice.
The six-month US trial gave the ring to 96 sexually active girls aged 15 to 17, who had not used it before.
Data presented at the IAS Conference on HIV Science, showed:
87% of the girls had detectable levels of the drug in their vagina
95% said the ring was easy to use
74% said they did not notice the ring in day-to-day life
There were some concerns before the trial that the girls' partners would not like the feel of the ring, but it reportedly enhanced pleasure.
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Prof Sharon Hillier, one of the researchers at the University of Pittsburgh School of Medicine, said: "HIV doesn't distinguish between a 16-year-old and an 18-year-old.
"Access to safe and effective HIV prevention shouldn't either, young women of all ages deserve to be protected."
There are now plans to test the ring with teenagers in Africa.
If the ring gets regulatory approval, it would be the first method of prevention exclusively for women.
bbc.co.uk/news/health-40715295