1453 Factors Influencing Long-Term Immunity Against Hepatitis B - the Role of Natural Boosters

Abstract

Background: Duration of protection against hepatitis B afforded by vaccination remains unknown. Factors influencing long-term immunity are uncertain.

Aim was to analyze factors influencing immunity against hepatitis B, including natural boosters, in 10-12-year old children vaccinated in infancy.

Methods: In 130 children aged 10-12 years, immunized against hepatitis B in infancy, exposure to risk factors for HBV infection (hospitalization, surgical and dental interventions, blood transfusion, HBV infection in family member, piercing) were analyzed. Humoral immunity (anti-HBs) and immune memory (anamnestic response to booster) were determined.

Results: Protective anti-HBs level was found in 102/130 (78%) children, in 43/130 (33%) titer was high (100-999 IU/l), in 16/130 (12%) very high (≥1000 IU/l). 28/130 (22%) had unprotective level, in 9/130 (7%) antibodies were undetectable. No statistically significant influence of age and gender on anti-HBs titer distribution (p< 0.28; p< 0.35) nor possession of unprotective antibody level (p< 0.329; p< 0.297) was found. Anamnestic response to booster was revealed in 12/16 (75%) and was positively correlated with younger age (p< 0,03), female gender (p< 0.01) and detectable prebooster anti-HBs (p< 0.02). Dental interventions and surgery had significant influence on possession of very high anti-HBs titers (p< 0.02; p< 0.05). Children who had blood transfusion in neonatal period, significantly more frequently had unprotective antibody levels (p< 0.01).

Conclusions: Immune memory is positively correlated with younger age, female gender and detectable anti-HBs. Natural boosters, especially dental and surgical interventions, may enhance the post-vaccination immunity. In children who received blood transfusion, immunization may be less effective.

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