Background: Immunization is the best method of protection against hepatitis B. Routine vaccination for newborns and infants was introduced in Poland in 1994-96. Although duration of protection afforded by vaccination remains unknown, no routine boosters are recommended. According to references, up to 50% of 15-year old children had lost the post vaccination immune memory protecting against HBV infection. The aim of the study was to determine the immunity against hepatitis B in 10-12-year old children and to establish indications for routine booster doses.
Material and methods: In 130 children aged 10-12 years, immunized against hepatitis B with recombinant vaccine in infancy (10 microg, according to schedule: 0-1-2-12 months, first dose given at birth) humoral immunity (anti-HBs antibodies) as well as cellular memory (anamnestic response to booster given in children without protective titers of anti-HBs) were determined. Titers of anti-HBs > or = 10 IU/l were considered protective. Anamnestic response was defined as increase in anti-HBs concentration from < 10 IU/l to > or = 10 IU/l 4 weeks after receiving a booster dose. MARKERS OF HBV INFECTION: hepatitis B surface antigen (HBsAg - marker of chronic hepatitis) and antibodies to core antigen (anti-HBc--marker of past HBV infection) were additionally determined.
Results: Protective level of anti-HBs was found in 102/130 (78%) children, including 43/130 (33%) with high (100-999 IU/l) and 16/130 (12%) with very high (> or = 1000 IU/l) titers. 28/ 130 (22%) did not have protective level of anti-HBs, in 9/130 (7%) antibodies were undetectable. Immune memory was determined in 9 children--anamnestic response was revealed in eight of them (89%). In 6/130 (4.5%) of participants HBV infection was confirmed according to positive anti-HBc, including 2 (1.5% of the study group) with positive HBsAg.
Conclusions: Most children in the studied group had seroprotection and immune memory against hepatitis B 10-12 years after vaccination. No routine booster seems to be necessary.