Intrapartum HIV Transmission Rates Halved By Adding Nevirapine

Combination treatment with nevirapine and zidovudine more effectively reduces intrapartum transmission rates of HIV than treatment with zidovudine alone, according to results of a new study by a National Institutes of Health research network. Previous studies have examined the effectiveness of postexposure prophylaxis in breast-fed infants born to women with HIV infection who did not receive antiretroviral therapy during pregnancy,^2,3,4 but this is the first study of postexposure prophylaxis in exclusively formula-fed infants from higher-income countries (United States, Brazil, Argentina, and South Africa).

Researchers compared the effectiveness of 3 treatments in reducing HIV type 1 transmission rates during the labor and delivery process, or the intrapartum period. The 3 treatments were the standard treatment of twice-daily zidovudine alone for 6 weeks; twice daily zidovudine for 6 weeks plus 3 doses of nevirapine in the first 6 days after birth; and twice-daily zidovudine for 6 weeks plus 2 weeks of treatment with nelfinavir and lamivudine.

Since some pregnant women do not know they have HIV infection or do not seek prenatal care, they do not receive the early treatment that would virtually eliminate the risk of HIV transmission to the fetus. In such cases, there is risk of HIV transmission to the neonate during the labor and delivery process. Newborns are most susceptible to HIV in their first 2 weeks of life. To minimize the risk of HIV transmission through breast milk, all newborns were formula-fed.

The rate of mother-to-child HIV transmission near the time of delivery was 2.2% among infants who received zidovudine plus nevirapine and 4.8% among infants who received zidovudine alone. A reduced rate of transmission (2.4%) was also noted in the 3-drug treatment group. However, the infants given all 3 medications were at increased risk for neutropenia compared with the infants given the 2-drug regimen. Additional benefits of the 2-drug regimen were that it was less costly and was easier to administer than the 3-drug regimen.

Pertinent Points:
- Combination antiretroviral regimens are more effective than zidovudine alone for prophylactic treatment of infants whose mothers did not receive antenatal antiretroviral therapy.
- Factors that increased risk of transmission were illegal drug use during pregnancy and a more severe HIV infection in the mother.

References:

1. Nielsen-Saines K, Watts H, Veloso VG, et al. Three postpartum antiretroviral regimens to prevent intrapartum HIV infection. N Engl J Med. 2012;366:2368-2379.
2. Chasela CS, Hudgens MG, Jamieson DJ, et al. Maternal or infant antiretroviral drugs to reduce HIV-1 transmission. N Engl J Med. 2010;362:2271-2281.
3. Gray GE, Urban M, Chersich MF, et al. A randomized trial of two postexposure prophylaxis regimens to reduce mother-to-child HIV-1 transmission in infants of untreated mothers. AIDS. 2005;19:1289-1297.
4. Taha TE, Kumwenda NI, Gibbons A, et al. Short postexposure prophylaxis in newborn babies to reduce mother-to-child transmission of HIV-1: NVAZ randomised clinical trial. Lancet. 2003;362:1171-1177.