Pre-exposure purified vero cell rabies vaccine and concomitant routine childhood vaccinations: 5-year post-vaccination follow-up study of an infant cohort in Vietnam

Children have a high risk of exposure to rabies in countrieswhere the disease is endemic. This prospective, 5-year studyfollowed two groups of children who had received diphtheria,tetanus, whole-cell pertussis and inactivated poliomyelitisvaccine (DTP-IPV) at 2, 3, 4 months and 1 year (Group B) orconcomitant with three doses of purified Vero cell rabies vaccine(PVRV), given at 2, 4 months and 1 year (Group A). Antibodydeterminations were made annually for 5 years. Data were availablefrom a total of 72 subjects; 30 in Group A and 32 in Group B.In Group A, the percentage of patients immunized against rabies(anti-rabies 0.5 IU/ml) decreased from 100% after the thirdvaccination to 63%, 5 years later. After 5 years, 93.8% in GroupA and 96.7% in Group B had seroprotective diphtheria antibodytiters 0.01 IU/ml, and all subjects had anti-polio (type 1,2 and 3) seroprotective titers 5 1:dil. We conclude that co-administrationof PVRV with DTP-IPV elicited protective antibody concentrationsto all antigens that persist for at least 5 years, with continuedprotection against rabies in over 60% of subjects. These resultsare consistent with integration of pre-exposure rabies vaccinationinto the Expanded Program on Immunization (EPI) in countrieswhere rabies is endemic.