Background:  Many programs encourage HIV-infected women living in low-resource settings to end breastfeeding earlier than usual. Early cessation of breastfeeding is intended to reduce postnatal HIV transmission while preserving benefits of breastfeeding for young infants. The Zambia Exclusive Breastfeeding Study (ZEBS) aimed to test whether or not there is net benefit of stopping breastfeeding abruptly at 4 months. 

Methods:  At 2 clinics in Lusaka, Zambia, 958 HIV-infected women and their infants were recruited prenatally, given single-dose nevirapine, and randomized postnatally into 1 of 2 groups: group A—abrupt cessation of breastfeeding at 4 months; or group B—continued breastfeeding for the duration of the mother’s informed choice. Exclusive breastfeeding (EBF) was promoted in both groups. Pairs were followed for 24 months and HIV infection was diagnosed by polymerase chain reaction. The primary outcome was HIV-free survival, and the follow-up to study end-point was 85%.   

Results:  By 24 months of age, there was no significant difference in HIV-free survival between the 2 randomized groups. Restricting to infants surviving HIV-uninfected at 4 months, 17% of 329 infants in group A and 19% of 331 infants in group B had HIV infection or had died by 24 months (p = 0.21). Among 153 infants with HIV infection by 4 months, there was a significant benefit for continued breastfeeding:  mortality was higher by 12 months in group A (57%) than in group B (29%, p = 0.01). In group A, 65% reported stopping all breastfeeding by 4 months. In group B, the median duration of breastfeeding was 16 months. In an as-practiced analysis, there was no significant difference in HIV-free survival between infants whose mothers complied with advice to stop breastfeeding. Among asymptomatic mothers with higher CD4 counts (>350), there was a trend towards better infant outcomes with longer breastfeeding (p = 0.06).

Conclusions:  Our results caution against early cessation of breastfeeding for HIV-infected women living in low-resource settings. In our study, stopping breastfeeding at 4 months resulted in less than anticipated reduction of HIV transmission, a benefit that was offset by increased mortality among uninfected infants. For HIV-infected infants, there was also a substantial mortality risk associated with stopping breastfeeding early. Programs providing HIV diagnosis services should strongly encourage breastfeeding into the 2^nd year of life for infants found to be HIV-infected.