Hepatitis B revaccination in healthy non-responder Chinese children: five-year follow-up of immune response and immunologic memory.

To assess persistence of anti-HBs and immunologic memory of non-responders after revaccination, 40 healthy non-responder children were given a three-dose recombinant hepatitis B vaccine revaccination randomly by intramuscular (10 microg per dose) or intradermal (2 microg per dose) route and followed up to five years. All 17 intramuscular and 22 of 23 intradermal children developed a seroprotective antibody response (anti-HBs>or=10 mIU/mL) after revaccination. Children of intramuscular group had significantly higher seroprotection rates and anti-HBs geometric mean titers than the intradermal group. At year 5, 50% of children in intramuscular group, but only 18.2% of intradermal group still maintained seroprotection (P=0.075). By the end of follow-up, a booster dose (5 microg) was given to those who had lost seroprotection. All the eight intramuscular children developed an anamnestic response with increase of anti-HBs level by 215 times, but two of the 18 intradermal children failed to produce seroprotective level. Three-routine-dose intramuscular revaccination was significantly more effective than low-dose intradermal revaccination with the same number of injections. No child seroconverted to HBsAg, and 11 had transient infections indicated by seroconversion to anti-HBc. These results demonstrated that non-responders could benefit from three doses intramuscular revaccination not only in high proportion of anti-HBs conversion but also in long-term persistence of seroprotection, and more importantly in preservation of the immunologic memory years after loss of protective anti-HBs.