Vaginal microbicides for preventing mother-to-child transmission of HIV infection - no evidence of an effect or evidence of no effect?

Background. Vaginal disinfection is a simple, potentially effective strategy for reducing mother-to-child transmission (MTCT) of HIV that can be implemented in combination with antiretroviral therapy or even in the absence of prenatal HIV testing. We systematically reviewed currently available randomised controlled trials to estimate the benefits and risks of this intervention. Methods. We conducted an exhaustive search for published and unpublished trials assessing the effect of vaginal microbicides on MTCT of HIV, extracted data in triplicate, assessed statistical heterogeneity between trial results, and conducted meta-analysis using Mantel-Haenszel's method. Findings. Five potentially eligible studies were identified, two of which met eligibility criteria. Pooling the data shows that the effect of vaginal disinfection on the risk of MTCT of HIV (relative risk (RR) 0.94, 95% confidence interval (CI) 0.71 - 1.25) and neonatal death (RR 1.36, 95% Cl 0.32 - 5.79) is uncertain. The combined data (two trials with 708 participants) had less than 80% power to detect a 30% reduction in the risk of MTCT of HIV from a baseline risk of 30%, and are compatible with a wide range of effects; from a 29% reduction to a 25% increase in risk. One trial, with 108 participants, showed no evidence that adverse effects increased in mothers (RR 1.02, 95% CI 0.87 1.20) and found that adverse effects decreased in neonates (RR 0.45, 95% CI 0.32 - 0.64). Interpretation. At present there is insufficient and inconclusive evidence on the effect of vaginal microbicides on the risk of MTCT of HIV. This review identifies the need and provides the impetus for an adequately powered randomised controlled trial to assess the effect(s) of this inexpensive intervention.