Background:  Single-dose nevirapine (sdNVP) is widely used to prevent mother-to-child HIV transmission (PMTCT) in resource limited settings. Given early detection of resistant mutants in a subset of mothers who receive sdNVP for PMTCT, concerns have arisen over potential reduced efficacy of sdNVP in subsequent pregnancies. The aim of this case-control study was to assess infant infection rates among women with prior sdNVP exposure (cases) compared to infants of NVP naïve pregnant women (controls) who receive sdNVP using a combined retrospective and prospective study design.

Methods:   Retrospective data were collected on Ugandan mothers who had taken sdNVP in the HIVNET 012 trial and who had a subsequent pregnancy where they also received sdNVP; compared to controls who received zidovudine (AZT) in the trial and then sdNVP in a later pregnancy, looking at infant infection outcomes in the latter pregnancy. For the prospective group, viral load, CD4 were gathered for pregnant women with a history of prior sdNVP compared to women who were NVP- naïve. Infant infection status was determined by at least two separate positive Roche 1.5 Amplicor DNA PCR results.

Results:  Final HIV infection status on 97 retrospective study infants; and 6 week infant infection status on 101 prospective study infants were available for this interim analysis. In the prospective group, there were no significant differences in enrollment maternal viral load, CD4 or age group between cases and controls. Adjusting for these variables in multivariate logistic regression revealed no statistically increased risk of HIV infection at 6 weeks for infants born to mothers with prior sdNVP exposure (OR 1.34, 95%CI 0.42 to 4.29).

Conclusions:  Based on both retrospective and prospective data including women from the HIVNET 012 trial, no increased risk of infant HIV infection was noted in subsequent pregnancies for Ugandan women with prior sdNPV exposure compared to NVP-naïve women.