Some epidemiological and laboratory studies have suggested that hormonal contraception can increase HIV transmission risk in women. There has been little research into the risk of transmission from women to men. To date findings have been inconsistent and WHO has called for high quality studies to look at potential interactions between hormonal contraception and HIV transmission.
Investigators from The Partners in Prevention HSV/HIV Transmission Study compared HIV incidence among women using hormonal contraception to those who were not. This analysis evaluated both HIV acquisition among women and transmission from women to men. Renee Heffron presented findings from this study in an oral presentation at IAS 2011.1
This was a prospective cohort study of 3790 serodiscordant couples from seven countries in East and southern Africa. The couples were enrolled from two studies conducted between 2004 and 2010, a randomised trial of acyclovir to reduce HIV transmission (n=3321) and a prospective cohort study of immune correlates of HIV protection (n=469).
They compared rates of HIV acquisition in women and HIV transmission from women to men using multivariate Cox proportional hazards regression and marginal structural modeling. The analyses were limited to infections acquired from the study partner (evaluated by viral genetic sequencing).
The negative partners were women in about a third (n=1314) of the couples evaluated, and two thirds (n=2476) were men.
Among the negative women, 21.2% overall used hormonal contraception at least once during follow up, of which 16% used injectable contraception at least once and 6.7% oral contraception. The HIV acquisition rates were 6.61 and 3.78 per 100 person-years in women currently using and not using hormonal contraception [AHR 1.98; 95%CI 1.06-3.68. p=0.03]. For injectable contraception the incidence rate was 6.85 per 100 person-years [AHR 2.05; 95%CI 1.06-3.68, p=0.04] and for oral contraception it was 5.94 per 100 person-years, [AHR 1.8 95%CI 0.55-5.82, p=0.33].
Overall, 33.3% of HIV-positive partners of negative men used hormonal contraception, 26.8% injectable and 8.9% oral. In these couples, HIV transmission rates from women to men were 2.61 and 1.51 per 100 person-years in those whose partners used and did not use hormonal contraception [AHR 1.91, 95%CI 1.12-3.45, p=0.02]. For injectable contraception the incidence rate was 2.64 per 100 patient years [AHR 1.95; 95%CI 1.06-3.58, p=0.03]. The incidence also increased in the group using oral contraception, 2.50 per 100 patient years, but as with HIV acquisition in negative women this did not reach statistical significance in this subgroup [AHR 2.09; 95%CI 0.75-5.84, p=0.16].
Results from marginal structural model analyses were consistent with those shown from the Cox proportional hazards regression.
When the investigators looked at this a possible explanation, there were significantly higher genital viral load concentrations overall in women using hormonal contraception [OR 1.51; 95%CI 1.13-2.01, p=0.01]. For injectable contraception these were significantly higher [OR 1.67; 95%CI 1.21-2.31, p=0.02]. But not for oral contraception [OR 1.06; 95%CI 0.62-1.84, p=0.49].
Dr Heffron noted that this was the first study to demonstrate that hormonal contraception increased an HIV-positive woman's risk of transmitting HIV to her partner.
She added that the benefits of effective hormonal contraception are unequivocal and must be balanced with the increase in risk of HIV infection. These possible risks should be discussed with women and couples alongside the importance of HIV prevention.
Strategies to improve access to and usage of lower dose and non-hormonal methods -- IUDs, implants, patches or combination injectables are warranted -- she concluded.
These findings understandably caused quite a stir and urgently need more investigation. This was followed by the report from Partners in Prevention that pregnancy doubles the risk of transmission from HIV-positive women to her male partner (to be reviewed in the next issue of HTB).2
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