ANTI-HBS RESPONSES IN CHILDREN VACCINATED WITH DIFFERENT SCHEDULES OFEITHER PLASMA-DERIVED OR HBV DNA RECOMBINANT VACCINE

This study evaluated the immunogenic and protective effects of plasma- derived and DNA recombinant anti-hepatitis B virus vaccines administer ed to infants at various ages and with different vaccination schedules : 3 monthly doses in the first 3 months of life, 3 doses (at 3, 5 and 11 months) or 2 doses (at 1 and 3 months) or 2 doses (at 3 and 5 month s). Anti-HBs (hepatitis B surface) and anti-HBc (hepatitis B core) mar kers were investigated twice: one month and ten years after vaccinatio n in 261 children immunized with plasma-derived vaccine, and one month and five years after vaccination in 449 children immunized with DNA r ecombinant vaccine. In all groups, the appearance of anti-HBs protecti ve levels one month after vaccination and their persistence in the fol lowing years were found in a larger number of subjects when the vaccin e doses had been administered after the third month of life rather tha n in the first three months. Moreover, our results show that the reapp earance of surface antibodies a week after the booster, in vaccinated children who became anti-HBs(-) in the years following vaccination, oc curred in a larger number of subjects when the primary vaccination wit h 3 doses had been performed in the first quarter or with 2 or 3 doses in the second quarter, in contrast, protective levels of anti-HBs wer e found in a small number of children belonging to the group vaccinate d with 2 doses in the first three months, and among them the majority seroconverted only one month after the booster. Anti-HBc was found 10 years after vaccination in only one child immunized with 2 doses of pl asma-derived vaccine, and 5 years after vaccination in two children im munized with 2 doses of DNA recombinant vaccine. All these children we re found to lose anti-HBs, and none of them had signs of disease or be came a carrier. Based on these results, the disappearance, in some chi ldren, of protective levels of anti-HBs in the years following vaccina tion does not mean the loss of anti-HBV protection. In fact, the trial showed that they reacted immediately to booster stimulation, demonstr ating a solid immunologic memory. Therefore, there may be no reason fo r giving booster injections when the vaccination of infants is carried out correctly.