Modeling vertical transmission of HIV: imperfect vaccines can be of benefit.

Reducing mother to child transmission (MTCT) of HIV in resource poor countries continues to be a major challenge. Here, we construct a hazard model to assess the effectiveness of combinations of HIV vaccine, Nevirapine (NVP), and HIV-specific monoclonal antibody (HIVAB) in reducing MTCT of HIV during the intrapartum and breastfeeding periods. The model shows that an intervention that uses three doses of vaccine with 30% initial immunity and 30% boost effect with subsequent doses (giving rise to maximum immunity approximately 66% with 3 doses) could reduce MTCT to 7.7% when used with NVP and to 5.9% when used with NVP and HIVAB. Using a vaccine with 50% initial immunity and 50% boost can reduce the rate to 4.3%. These results indicate that even an imperfect vaccine, when used in combination with other therapies, can be of considerable benefit in preventing MTCT in resource poor countries.