AIDS 2012 Conference News: Further Analysis Shows Higher HIV Risk With Injectable Contraception

Confirming results of an earlier large cohort study (Heffron R et al, Lancet Infectious Diseases. 2012;12:19-26), several sensitivity analyses determined that use of injectable hormonal contraceptive doubles the risk of HIV acquisition by African women with an HIV-positive partner, compared with use of no hormonal contraceptive. When the analysis focused on presumed consistent DMPA users, injectable contraceptive use more than tripled the risk of HIV infection.

Reliable contraception is essential to family planning, and injectable hormonal contraception is favored by many women because of its simplicity and durability. In February 2012, after considering the published study by this group and other work, the World Health Organization (WHO) maintained its advice not to restrict use of hormonal contraceptives to avoid unintended pregnancies. Women using progestogen-only injectable contraceptives, WHO advised, should also use condoms or other measures to prevent HIV infection.

At AIDS 2012, Heffron and colleagues reported results of additional sensitivity analyses to test the strength of the original finding. These Cox proportional hazards regression models considered the impact of age, the HIV-positive male partner’s viral load, and time-dependent unprotected sex and pregnancy. The analyses compared HIV incidence (new infections) in women using injectable hormonal contraception versus women using no hormonal method.

In every sensitivity analysis, hormonal contraceptive use at least doubled the risk of HIV acquisition by women with a positive partner. A statistical model adjusted for coital frequency confirmed a doubled risk of HIV infection with injectable contraceptive use versus no hormonal contraceptives (adjusted hazard ratio [aHR] 2.06, 95% confidence interval [CI] 1.04 to 4.07, P = 0.04). In a model adjusted for the male partner’s report of sex without a condom, the woman’s HIV risk with injectable contraceptives remained doubled (aHR 2.03, 95% CI 0.95 to 4.32, P = 0.07).

When the researchers limited the analysis to a subgroup of women who reported unprotected (condom-free) sex, HIV risk with injectable hormones was more than doubled (aHR 2.29, 95% CI 0.70 to 7.53, P = 0.17), as it was during periods that included only visits before a first switch in contraceptive methods (aHR 2.62, 95% CI 0.93 to 7.33, P = 0.07).

A final analysis focused only on presumed consistent DMPA users and thus eliminated women from South Africa. In this model, injectable contraception more than tripled chances of HIV infection when compared with use of no hormonal contraception (aHR 3.39, 95% CI 1.38 to 11.22, P = 0.01).

The researchers note that some associations had P values greater than 0.05 because of reduced statistical power in these analyses, “but the magnitude of association continued to be as strong as that seen in our primary analytic model.”

At AIDS 2012, a separate systematic review of research on hormonal contraception and HIV acquisition found no association between oral contraceptive use and HIV risk. As for injectable hormonal contraceptives, the researchers conclude that “evidence assessing DMPA or non-specified injectable contraception and risk of HIV acquisition is inconsistent; it does not establish a clear causal association with HIV acquisition, nor does it definitively rule out the possibility of an effect.”

Sources:

R. Heffron, D. Donnell, H. Rees, C. Celum, N. Mugo, E. Were, G. de Bruyn, E. Nakku-Joloba, K. Ngure, J. Kiarie, R. Coombs, J. Baeten, Partners in Prevention HSV/HIV Transmission Study Team. Association of injectable contraception and risk of HIV-1 acquisition in women in HIV-1 serodiscordant partnerships: persistence of effect in multiple sensitivity analyses. XIX International AIDS Conference. 22-27 July 2012. Washington, DC. Abstract WEAC0202.
C. Polis, K. Curtis. Hormonal contraception and HIV acquisition in women: a systematic review of the epidemiological evidence. XIX International AIDS Conference. 22-27 July 2012. Washington, DC. Abstract WEAC0203.

For the WHO technical statement on hormonal contraception

Written by Mark Mascolini on behalf of the International AIDS Society