Serologic response to rabies pre-exposure vaccination in persons with potential occupational exposure in Singapore

Sixty-six animal workers received primary rabies vaccination with purified Vero cell vaccine (PVRV, Verorab). One year later, 26 (39%) demonstrated antibody titers below the recommended minimum of 0.5 IU/ml, and required a booster. All 15 of a separate group reporting primary vaccination with at least one booster had titers above 0.5 IU/ml 1 year later, demonstrating long-term boostable immunity. Rabies antibody titers should be checked 1 year after primary rabies vaccination in persons at high risk of frequent rabies exposure. If access to serological surveillance is unavailable, such high-risk individuals should receive booster vaccination.