A hormone shot commonly given to women in Eastern and Southern Africa every three months to prevent pregnancy may double the women’s risk of becoming infected with H.I.V., according to a study published Monday.
The study also found that when the same contraceptive is used by women who are already H.I.V.-positive, their male partners are twice as likely to contract the disease than if the women used no contraception.
According to the data, women using hormonal contraception became infected at nearly twice the rate of those not using that method and transmission of H.I.V. to men occurred at a similar rate.
The study, published in The Lancet Infectious Diseases, was conducted by researchers from the University of Washington and involved 3,800 couples in Botswana, Kenya, Rwanda, South Africa, Tanzania, Uganda and Zambia. At least one person in each couple was already infected with H.I.V. when the study began. Over two years, researchers documented their contraception methods and tracked whether the uninfected partner contracted H.I.V. from the infected partner.
Although authors of the study guessed that the injectable contraception used by the African women were generic versions, the branded drug in question is Pfizer’s Depo-Provera. According to the New York Times, Pfizer declined to comment on the study, saying officials had not yet read it.
Why the injectable hormones seem to raise H.I.V. risk is still inconclusive. However, the study’s authors say that before any warnings are made, greater emphasis should be placed on encouraging H.I.V positive individuals to use condoms in addition to hormonal methods of birth control.

Photo: Chaiwat Subprasom / Reuters