Don't Get Stuck With HIV

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Hormone injections increase women’s risk to get HIV

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Many studies have followed HIV-negative women in Africa, testing them from time to time to see who gets HIV, and asking about various risks. At least 10 such studies asked women about their birth control practices – injected hormones vs. other or no methods – and recorded at least 10 new HIV infections in women using injected hormones. In 9 of 10 studies, women who used hormone injections were 1.2 to 10.4 times more likely to get HIV than other women (see Table below).

These studies, which show that hormone injections increase women’s risk to get HIV, do not show why or how that happens. Two possible ways this could happen are:

1. The injections may be giving women HIV through reused syringes and/or needles or through contaminated multi-dose vials. Because reuse would be more in some places and less in others, this would explain why women’s risks with hormone injections seem to be greater in some studies than in others (especially in Malawi in 2003-05; see Table below).

2. The injected hormones may cause changes in women’s bodies that increase their risk to get HIV whenever they are exposed. For example, the hormones may thin a woman’s vaginal wall, so that having sex with an HIV-positive man is more dangerous. Or the hormone may influence cells anywhere in a woman’s body (not only in her vagina) to multiply HIV from any source — from sex or blood contact. This could make it easier for women to get HIV not only from sex but also from unsterile instruments during dental care, hair-dressing, manicures, etc.

Wherea the first risk can be addressed by ensuring a safe injection, the second risk cannot, because it comes from the hormones. Unsafe injections might explain some of the findings reported in the Table below. However, in the study of HIV transmission from known HIV-positive husbands (Botswana, Kenya, and 5 other countries, 2004-10) it seems clear that injected hormones enhanced women’s “uptake” of HIV from sexual exposures.

The evidence that progesterone increases women’s risk for HIV agrees with findings from animal studies. As early as 1996, scientists reported that giving monkeys progesterone implants (the same hormone injected into humans for birth control) increased by 8 times the monkeys’ risk to get SIV (monkeys’ HIV) infections through the vagina.[i] 

Table: Evidence that taking hormone injections for birth control increases women’s risk to get HIV

Country, year Women followed Women’s relative risk to get HIV with vs. without hormone injections Groups of women compared
Kenya, 1993-2003[ii] 1,206 prostitute women 1.79 Hormone injections vs. no hormones for birth control
Uganda, 1994-99[iii] 5,117 women from the general population 0.8 Hormone injections vs. no hormones or condoms for birth control
South Africa, 1999-2002[iv] 634 women from family planning clinics 1.76 Net-En injections vs. no hormones for birth control
Uganda and Zimbabwe, 1999-2004[v] 4,541 mostly (91%) low risk women 1.25 Hormone injections vs. no hormones for birth control
South Africa, 2000-2004[vi] 4,200 low risk women 1.21 DMPA injections vs. no hormones for birth control
Malawi, 2003-05[vii][viii] 787 post-partum women and women from family planning clinics 10.42 DMPA injections vs. no DMPA injections
South Africa and Zimbabwe, 2003-06[ix] 4,948 low risk women 1.66 Hormone injections vs. no hormone injections
South Africa, 2004-07[x] 5,567 low risk women 1.28 DMPA vs. no hormonal contraception
Women aged <25 years 1.68
South Africa, 2005-09[xi] 2,236 low risk women 1.72 Hormone injections vs. no hormonal contraception
Botswana, Kenya, Rwanda, South Africa, Tanzania, Uganda, Zambia, 2004-10[xii] 1,314 women with HIV-positive husbands 2.19 Hormone injections vs. no hormonal contraception

DMPA: depo-medroxyprogesterone acetate, Net-En: norethisterone enanthate.

Note: This list excludes studies with less than 10 new infections in women using hormone injections. In studies with few infections, the results may be statistical accidents.


[i] Marx PA, Spira AI, Gettie A, et al. Progesterone implants enhance SIV vaginal transmission and early virus load. Nature Med 1996; 2: 1084-1089.

[ii] Baeten JM, Benki S, Chohan V, et al. Hormonal contraception use, herpes simplex virus infection, and risk of HIV-1 acquisition among Kenyan women. AIDS 2007; 21: 1771-1777.

[iii] Kiddugavu M, Makumbi F, Wawer MJ, et al. Hormonal contraceptive use and HIV-1 infection in a population -based cohort in Rakai, Uganda. AIDS 2003; 17: 233-240.

[iv] Kleinschmidt I, Rees H, Delany S, et al. Injectable progestin contraceptive use and risk of HIV infection in a South African family planning cohort. Contraception 2007; 75: 461-467.

[v] Morrison CS, Richardson BA, Mmiro F, et al. Hormonal contraception and the risk of HIV acquisition. AIDS 2007; 21: 85-95.

[vi] Myer L, Denny L, Wright TC, Kuhn L. Prospective study of hormonal contraception and women’s risk of HIV infection in South Africa. Int J Epidemiol 2007; 36: 166-174.

[vii] Kumwenda NI, Kumwenda J, Kafulafula G, et al. HIV-1 incidence among women of reproductive age in Malawi. Int J STD AIDS 2008; 19: 339-341.

[viii] Kumwenda JJ, Makanani B, Taulo F, et al. Natural history and risk factors associated with early and established HIV type 1 infection among reproductive-age women in Malawi. Clin Infect Dis 2008;46:1913–20.

[ix] Padian NS, van der Straten A, Ramjee G, et al. Diaphragm and lubricant gel for prevention of HIV acquisition in southern African women: a randomized controlled trial. Lancet 2007; 370: 251-261.

[x] Morrison CS, Skoler-Karpoff S, Kwok C, et al. Hormonal contraception and the risk of HIV acquisition among women in South Africa. AIDS 2012; 25: epub ahead of print.

[xi] Wand H, Ramjee G. The effects of injectable hormonal contraceptives on HIV seroconversion and on sexually transmitted infections. AIDS 2012; 26: 375-380

[xii] Heffron R, Donnell D, Rees H, et al. Use of hormonal contraceptives and risk of HIV-1 transmission: a prospective study. Lancet Infect Dis 2012: 12: 19-26.

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