Rabies Neutralizing Antibody: Inadequate Response to Equine Antiserum and Duck-Embryo Vaccine

After exposure to a patient with rabies, 15 hospital staff members received equine antiserum to rabies and duck-embryo rabies vaccine (DEV). Three persons (20%) had a low (<1:5) or absent serum neutralizing-antibody (SN) response 15 days after treatment began. Sixty-six days after treatment began, six of 13 (46%) had absent or only a low SN response. Forty percent of patients who received both recommended boosters had SN titers at day 66 as low as those who received neither booster. These data indicate that DEV is a poor antigen when combined with horse serum even when prescribed DEV boosters are given. The antibody response of patients given equine antiserum to rabies and DEV should be determined since additional DEV boosters may be required.