Immunization Status Against Hepatitis B Among Iranian Junior Medical, Nursing, and Obstetrics Students With Different Vaccination Patterns

Abstract

Background: Since the protection time by hepatitis B (HB) vaccination is unclear, the strategy of immunization of junior students who previously received hepatitis vaccine is controversial. Objectives: This study aimed to determine the status of immunity to hepatitis B in junior medical, nursing and obstetrics students with different hepatitis B virus (HBV) vaccination patterns. Patients and Methods: In an analytical cross-sectional study, 255 junior medical sciences students were tested for quantitative antibodies to hepatitis B surface antigen (anti-HBs). The proportion of protective immunity was compared in different vaccination patterns. Results: Vaccination coverage rates were 74.1%. About half the participants didn’t show serological evidence of protective immunity; 68.9% had their last shot more than 10 years ago and 30.4% had a vaccination history of five years or less (P < 0.001). Geometric mean level of anti-HBs titer among students, who had received a primary series vaccine at birth, was significantly lower than students who had started vaccination at an older age (P < 0.001). Also, analysis of variance for geometric mean of anti-HBs titer showed significant differences between groups based on injection time from the last shot (P < 0.001) (post hoc comparisons resulted in a P value of < 0.001 for birth versus < 5 year group, and P < 0.001 for the 5 to 10 year group). The lowest rate of non-protective level belonged to participants with complete three doses and a booster additional shot (27.1%). The final model for independent predictors of anti-HBs positive status was made by a binary logistic regression analysis. The model included presence of a booster dose, injection time from last shot, and discipline of study. Conclusions: This study shows lower anti-HBs among students who were vaccinated at infancy compared to those vaccinated at older childhood or adolescence. Also, subsequent measurement of anti-HBs level at the time of entrance to university is recommended for all previously immunized students. Keywords: Hepatitis B; Vaccination; Medical Student; Antibody; Protective Immunity