In the PEPI-Malawi trial, most women received single dose nevirapine (sdNVP) at delivery, and infants in the extended study arms received sdNVP plus 1 week of daily zidovudine (ZDV), followed by either extended daily NVP or extended daily NVP+ZDV up to 14 weeks of age. While extended NVP prophylaxis reduces the risk of postnatal HIV transmission, it may increase the risk of NVP resistance among infants who are HIV-infected despite prophylaxis.
We analyzed 88 infants in the PEPI- Malawi trial with in utero HIV infection who received prophylaxis for a median of 6 weeks prior to HIV diagnosis. HIV genotyping was performed using the ViroSeq HIV Genotyping System.
At 14 weeks of age, the proportion of infants with NVP resistance was lower in the extended NVP+ZDV arm than in the extended NVP arm (28/45=62.2% vs. 37/43=86.0%, p=0.015). None of the infants had ZDV resistance. Addition of extended ZDV to extended NVP was associated with reduced risk of NVP resistance at 14 weeks if prophylaxis was stopped by 6 weeks (54.5% vs. 85.7%, p=0.007), but not if prophylaxis was continued beyond 6 weeks (83.3% vs. 87.5%, p=1.00).
Addition of extended ZDV to extended NVP prophylaxis significantly reduced the risk of NVP resistance at 14 weeks in infants with in utero HIV infection, provided that HIV infection was diagnosed and the prophylaxis was stopped by 6 weeks of age.