Booster hepatitis B vaccination not necessary for long-term protection in children immunised with hexavalent vaccines.

Abstract

< 0.0001). Geometric mean concentration (GMC) was lower among children primed with Hexavac than among those primed with Infanrix Hexa (p < 0.0001). In the multivariate analysis the type of hexavalent vaccine given was the only determinant of anti-HBs concentration after adjustment. However, children in both groups who received a booster hepatitis B vaccination had a similar rapid anamnestic response, and the proportion of children who responded to the booster were similar between groups. 92.1% of children originally given Hexavac and 94.3% of children originally given Infanrix Hexa showed protective levels of antibodies after the booster vaccination, thus showing the presence of specific immune memory. Side-effects were infrequent, mild, and did not differ between the two booster groups. No serious adverse events were reported. These results suggest that infant immune systems are able to recall responding to hepatitis B more than 5 years after primary immunisation with hexavalent vaccines, thereby providing effective protection even in children showing low (< 10 mIU/ml) or undetectable levels of antibodies. Together, these findings suggest that in healthy children the immunological memory for hepatitis B surface antigen (HBsAg) may outlast the presence of antibody. In other words, children who have lost preventive antibody concentrations might still maintain T-cell memory that is able to trigger anti-HBs production by B cells when activated by revaccination