UNICEF said there were some 2.1 million adolescents living with HIV last year, half of whom were in six countries. Last year, about two-thirds of new HIV infections in adolescents aged 15 to 19 were among girls.

The report showed that by increasing investment in high-impact interventions to about 5.5 billion U.S. dollars by next year, 2 million adolescents, particularly girls, could avoid getting infected by 2020.

"If high-impact interventions are scaled up using an integrated approach, we can halve the number of new infections among adolescents by 2020," said Lake. "It's a matter of reaching the most vulnerable adolescents with effective programs -- urgently."

High-impact interventions include condoms, antiretroviral treatment, prevention of mother-to-child transmission, voluntary medical male circumcision, communications for behavior change, and targeted approaches for at-risk and marginalized populations. They go hand in hand with investments in other sectors such as education, social protection and welfare, and strengthening health systems, the UNICEF report pointed out.

The new report also stressed the need to ensure that more children living with HIV receive antiretroviral treatment, and to apply the knowledge that already exists and pursue new innovations to turn the vision of an AIDS-free generation into reality.

"The world now has the experience and the tools to achieve an AIDS-free generation. Children should be the first to benefit from our successes in defeating HIV, and the last to suffer when we fall short," said Lake.