Control of sexually transmitted infections for HIV prevention

Abstract

Ronald Gray and Maria Wawer1 argue that promoting control of sexually transmitted infections (STIs) as an HIV prevention strategy diverts funds from proven efficacious interventions and should cease. We argue against such a policy change. Modelling shows that the relative effect of bacterial STI control decreases during HIV epidemics as HIV spreads from core groups to individuals with lower STI rates and due to behavioural risk reduction.2 This projection is consistent with empirical evidence of a large effect of bacterial STI control in early-phase HIV epidemics.3 Subsequent trials of bacterial STI control in late-phase generalised epidemics have not been powered to detect the smaller relative effects predicted by models. Modelling also indicates that bacterial STI control could remain cost effective in high HIV-incidence populations since its absolute effect (infections averted) is large even if the relative effect is low.4 Furthermore in mature HIV epidemics herpes simplex virus type 2 (HSV-2) increasingly dominates as a cause of STIs. Epidemiological evidence that infection with HSV-2 enhances HIV spread remains strong and trials of HSV-2 suppression showed significant reductions in plasma and genital HIV viral load.5 The search for effective HSV-2 interventions must continue. Aside from bacterial STI treatment the only intervention shown in randomised controlled trials to reduce HIV incidence is male circumcision. We fully support efforts to scale up circumcision services but history shows there is no magic bullet for HIV prevention in Africa. Relaxation of STI control could lead to increased STI rates and enhanced HIV transmission. To cease funding for one of the few strategies that could contribute to HIV control would be as inadvisable as relaxing blood screening because few HIV infections are attributable to transfusions. (full-text)