In a randomized trial comparing nevirapine ( NVP ) - based versus lopinavir/ritonavir ( LPV/r ) - based antiretroviral therapy ( ART ) in HIV-infected children [ primary endpoint discontinuation of study treatment for any reason or virologic failure by week 24 ] aged 2 months to 3 years , we assessed whether clinical , virologic , immunologic and safety outcomes varied by prior single-dose NVP exposure ( PrNVP ) for prevention of mother-to-child HIV transmission and other covariates .