[Influence of natural boosters on long-term immunity against hepatitis B]

Incidence of hepatitis B in Poland decreased significantly after implementation of routine immunization in infants. Natural boosters may influence the long-term post vaccination immunity in countries, where endemicity is high. In areas of low incidence this influence may be limited. The aim of the study was to analyze the influence of risk factors for HBV infection (potential natural boosters) on long-term post vaccination immunity against hepatitis B and the possibilityof HBVinfection in previously vaccinated individuals.

In 130 children aged 10-12years, vaccinated with 4 doses ofrecombinantvaccine against hepatitis B in infancy, exposure to risk factors for HBV infection (infection in family members including mother, hospitalization, surgical interventions, blood transfusion, dental treatment, piercing, tattooing) was analyzed. Markers of HBVinfection (anti-HBc and HBsAg) and humoral immunity against hepatitis B were determined. Protective level of anti-HBs antibodies was defined as > or =10 IU/1.

Statistically significant influence of dental treatment (p<0.02) andsurgicalinterventions (p<0.05) on possessing very high anti-HBs titer (> or = 1000 IU/) was revealed, which indicates that these factors act as natural boosters. Children, who previously received blood transfusion, statistically more frequently did not have protective level of anti-HBs (p<0.0 I). In all 6 children with confirmed HBV infection there was exposure to risk factors for infection in anamnesis. In children with chronic hepatitis B (positive HBsAg) statistically significantly more frequently surgical interventions were performed (p<0.05).

I. Despite of low incidence of hepatitis B in Poland, natural boosters, especially dental and surgical treatment, may stimulate the post vaccination immunity. 2. Blood transfusion is currently not a source of infection, however, children who received blood transfusion in the neonatal period, may require control of immunization efficacy or a booster dose. 3. HBVinfection and chronic hepatitis B may occur in previously vaccinated children, especially if they underwent surgical intervention.