Incidence and variables associated with inadequate antibody titers after pre-exposure rabies vaccination among veterinary medical students

Background: This study sought to determine the proportion of subjects with inadequate antibody titers at two years after pre-exposure rabies vaccination and identify variables associated with inadequate antibody titers. Methods: A retrospective chart review of vaccination records of veterinary students in Michigan, 2004-2009, was conducted. Antibody titers <0.5. IU/ml as estimated by rapid fluorescent focus inhibition test were classified as inadequate. Variables were compared between the two groups to identify factors associated with inadequate titers at two years. Results: A total of 603 subjects (mean age 24.1. ±. 4.2 years, male:female 106:497) were included. Nearly one third (177/603, 29.4%) had inadequate titers at two years. Male gender (adjusted odds ratio (AOR) 1.87, 1.07-3.27; p= 0.029), vaccine manufacturer (AOR 1.49, 1.16-1.92; p= 0.002), BMI >25 (AOR 1.61, 1.02-2.54; p= 0.043), and duration between first and third doses of vaccine >21 days (AOR 2.49, 1.26-4.97; p= 0.009) were independently associated with inadequate titers. Conclusions: Twenty-nine percent of subjects had inadequate antibody titers against rabies at 2 years. Gender, vaccine type/manufacturer, BMI of 25 or greater, and more than 21 days between the first and third doses of vaccine were independently associated with inadequate antibody titers at two years. Our data would support modifying the recommendations, so the third dose is recommended at 21 days rather than 21-28 days.