Objective To examine the emergence and fading of NVP resistance (NVP R) mutations in HIV-1-infected Ugandan women and infants who received single dose NVP to prevent HIV-1 vertical transmission.

Design We examined NVP R in women and infants who received NVP in the HIVNET 012 clinical trial, including 41 out of 48 women with infected infants, 70 randomly-selected women with uninfected infants, and 33 out of 49 infected infants.

Methods Plasma HIV-1 was analyzed using the Applied Biosystems ViroSeq HIV-1 Genotyping System.

Results NVP R mutations were detected in 21 out of 111 (19%) women tested 6–8 weeks after delivery. The rate of NVP R was similar among women whose infants were or were not HIV-1 infected. K103N was the most common mutation detected. NVP R mutations faded from detection within 12–24 months in all 11 evaluable women. High baseline viral load and low baseline CD4 cell count were associated with development of NVP R. NVP R mutations were detected in 11 out of 24 (46%) evaluable infants who were infected by 6–8 weeks of age. The most common NVP R mutation detected in infants was Y181C. Those mutations faded from detection by 12 months of age in all seven evaluable infants. Of nine evaluable infants with late HIV-1 infection, only one had evidence of NVP R.

Conclusions NVP R was detected more frequently in infants than women following NVP prophylaxis, and different patterns of NVP R mutations were detected in women versus infants. NVP R was detected infrequently in infants with late HIV-1 infection. NVP-resistant HIV-1 faded from detection in women and infants over time.