Hepatitis B vaccine and the need for a booster dose after primary vaccination

Objectives: Protective antibodies levels, induced by Hepatitis B virus (HBV) vaccine, persist for long-term after primary immunization, but there is evidence that, as the time since vaccination increases, there is a reduced ability to maintain immune memory. The study aim was to determine the prevalence and the duration of persistence of an anti-HBs titer with ≥10 mIU/mL and eventual predictors of reduced seroprotection. Methods: The study was conducted among students attending medical and healthcare professions schools from January 2014 to June 2016. Data were collected through the review of medical records completed during the medical surveillance visit. All subjects had received HBV vaccine according to the Italian Ministry of Health indications. Results: The results are reported for 722 subjects. Positive anti-HBs titer was found in 72.6% (95% CI = 69–76). The mean age of the subjects was 25.5 years. Subjects vaccinated during adolescence and students that had received an adult vaccine dose were significantly more likely to be seroprotected. The longer the time interval since vaccination the lower the probability of being seroprotected; however if the role of time since vaccination was considered after stratification by vaccine dose, a statistically significant association with a lower percentage of seroprotected remains only in the subgroup of subjects who received the pediatric dose. The findings of the multivariate regression analysis partially confirmed those of the univariate analysis. Conclusions: In conclusion, our findings show that over 25% of HBV vaccine recipients had an antiHBs titer <10 mIU/ml after 18 years of more from the primary vaccination. Furthermore, in the case a booster dose would be needed, our results suggest that the vaccination strategy should prefer administration of a vaccine adult dose during early adolescence, since it might offer longer-term protection through adulthood.