Pre-Exposure Rabies Immunization with Human Diploid Cell Vaccine: Decreased Antibody Responses in Persons Immunized in Developing Countries

Abstract In November 1982, a U.S. Peace Corps volunteer in Kenya completed pre-exposure rabies prophylaxis with a standard 3 dose intradermal (ID) series of human diploid cell rabies vaccine (HDCV). In May 1983, she was bitten by a dog and died of rabies 3 months later. An initial investigation revealed that the patient, as well as 9 of 11 others immunized at the same time, had no rabies antibody titers ( 0.15); however, groups immunized in the United States had significantly higher titers than a group of Kenyan nationals (P ≤ 0.0001), and the Kenyans had significantly higher titers than 2 Peace Corps groups immunized in Kenya (P ≤ 0.0001). No single hypothesis proposed (laboratory error, vaccine potency, vaccination technique, or specific immune suppression) accounted for the observed differences. Although we cannot fully explain the poor response to HDCV, it is probably due to multiple factors. We conclude that persons immunized with ID pre-exposure HDCV in developing countries should have rabies antibody titers determined to ensure their seroconversion; for persons immunized in the United States, such titers need not be routinely determined.