Government grants in South Africa are helping poor girls resist the advances of older men, reducing the risk of getting HIV, a study says.
The Oxford University study found that girls from homes which received child support grants were two-thirds less likely to date older men for money.
Young girls are up to three times more likely to become infected with HIV than boys in South Africa, experts say.
Local officials see "sugar daddies" as a major factor in the spread of Aids.
South Africa has more people living with HIV than any other country.
A team of researchers from universities including UK's Oxford University and South Africa's Witwatersrand University interviewed more than 3,500 teenagers from two provinces in the country over a period of three years.
According to the study, teenage girls from households which received child support grants are less likely to sleep with an older man in exchange for money, food or school fees than those from homes which did not receive the benefit.
"This study shows that as long as they are given enough money to survive, girls will choose not to have a sugar daddy," said Lucie Cluver of the University of Oxford.
The study, published in the medical journal, Lancet Health Global Health, found that around 15% of teenagers were engaging in risky sexual behaviour such as unprotected sex, multiple partners or sex while under the influence of drugs or alcohol.
"Child support grants do not make teenagers more sensible when it comes to safer sex," said Mark Orkin from the University of the Witwatersrand, in a statement.
"But what they can do is to provide enough financial security for girls that they do not have to choose their sexual partners through economic necessity," he said.
Granting a better future?
Health Minister Aaron Motsoaledi recently identified "sugar daddies" as one of the biggest threats to the country's attempts to curb the spread of Aids.
Because of the skewed balance of power in many of these relationships, girls are often pressured to have sex without a condom, says the BBC's Pumza Fihlani in Johannesburg.
But this study seems to suggest that these government grants are slowly empowering teenagers in poor communities, who are most at risk.
"It also shows how valuable it is to give [grants] not only to younger children but also to teenagers, who are most at risk of HIV infections," said Ms Cluver.
South Africa has one of the world's highest HIV infection rates and currently runs the world's largest antiretroviral program.
Local experts say new infections have decreased in recent years, which could indicate that young people are changing their sexual behaviour.
About 11 million children are currently receiving a child support grant, which is given to poor families who have shown that they are struggling to survive.
Each eligible child receives a monthly grant of 300 rand ($30; £19) and a foster child grant of 800 rand.