Seroprevalence of anti-HBs antibodies at young adulthood, before and after a booster vaccine dose, among medical personnel vaccinated in infancy.

Background: Questions remain regarding the long-term protection provided by childhood HBV vaccination. The goals of this study were to assess HBV seroprevalence among medical personnel purportedly vaccinated in infancy; to investigate the immune response after a booster dose given in young adulthood; and to identify predictors of non-responders.

Methods: Between 2011 and 2013 we studied Israeli male military recruits purportedly vaccinated in infancy. All subjects were born after January 1st 1992 and were undergoing medic training. We collected personal data and blood samples at baseline, and administered a dose of HBV vaccine. Subjects were retested one month later and received a second dose. A third blood draw was conducted one month after the second dose. Data collected at baseline were used as predictor variables of seropositivity (anti-HBs≥10mIU/ml).

Results: 617 subjects were available for baseline analysis and 539 for paired observations at one month. Baseline seropositivity was 33.7%. Subjects who received post-infancy vaccine doses had a seropositivity rate double that of those denying additional doses (RR 2.22, 95% CI 1.55-3.18). One month after the first booster dose, the overall cumulative population seropositivity reached 87.7%. One month after the second vaccine dose, population seropositivity was 97.9%. Heavy smokers were 5 times less likely to demonstrate detectable antibodies after a single booster dose (OR 0.196, 95% CI 0.060-0.641, P=0.007).

Conclusions: This population-based study is important for informing public health vaccination policy. Our results strongly indicate that among cohorts vaccinated in infancy, two doses in adulthood will provide maximal protective antibody levels, while one dose will provide sufficient population protection.