Antibody response following rabies vaccination: a retrospective cohort study from a tertiary centre in Kerala, India

BACKGROUND: Globally accelerated efforts are underway to eliminate dog-mediated rabies, underscoring the importance of effective anti-rabies prophylaxis. This study aims to assess the antibody response and its long-term persistence following rabies vaccination, their determinants, and suggest the optimal timing for a booster dose. METHODS: We performed a retrospective cohort study among 150 participants, at the preventive clinic of Government Medical College, Thiruvananthapuram. Anti-rabies antibody titer in serum samples was estimated with the Rapid Fluorescent Foci Inhibition Test. To estimate the optimal timing for booster doses, the receiver operating characteristic (ROC) curve was plotted. RESULTS: Protective antibody titers (0.5 IU/ml) were observed in 92.7% of participants, with a mean titer of 3.81 (3.31) IU/ml. ROC analysis identified 5 years as a cut-off for booster dose. Regression analysis indicated a shorter time duration since last vaccination (P = .003) and intramuscular route (P = .005) as predictors of high antibody titers. However, the achievement of protective antibody titer was comparable for intramuscular and intradermal schedules. CONCLUSIONS: Achievement of protective antibody titers is universal and long-lasting following anti-rabies vaccination, irrespective of the route of vaccination. Five years since the last dose could be used as an optimal cut-off for booster dose.