Randomized, single-blind comparison of the immunogenicity and reactogenicity of 20 micrograms and 10 micrograms doses of hepatitis B vaccine in adolescents.

The study compares the effect of two different doses of a recombinant DNA hepatitis B vaccine (Engerix-B) administered to 320 healthy adolescents divided randomly into two equal groups, using the 0, 1 and 6 month's vaccination schedule. Initially the larger dose elicited protective levels of antibody in a greater proportion of subjects. The seroprotection rates were significantly higher at both months 1 (17.6% v/s 9.2%) and 2 (68.8% v/s 56.7%). The difference was especially relevant 6 months after the start of the vaccination schedule when a 92.4% seroprotection rate was obtained in the 20 micrograms dose group, whereas only 78.3% of subjects in the 10 micrograms dose group had protective antibody levels. Furthermore there were significant differences in anti-HBs geometric mean titers for seroconverters at months 6 (109 v/s 56mlU/ml) and 7 (4774 v/s 2705mlU/ml). However one month after the third vaccine administration, both doses produced similar high seroprotection rates (97.9% and 97.1%, respectively). The difference in the generally mild overall reactogenicity for the 2 dose levels was not remarkable although the higher dose produced more local symptoms. The conclusion from the study was that the 10 micrograms dose produces a very good antibody response in adolescents, provided the full vaccination course of three doses, according to a 0, 1 and 6 month's schedule, is administered. However, the 20 micrograms dose should be used if compliance to the full course is in doubt since a 92.4% seroprotection rate can be obtained with 2 injections compared to only 78.3% with the 10 micrograms dose.

A Thai boy with hereditary enzymopenic methemoglobinemia type II.

Individuals with methemoglobin exceeding 1.5 g/dl have clinically obvious central cyanosis. Hereditary methemoglobinemia is due either to autosomal dominant M hemoglobins or to autosomal recessive enzymopenic methemoglobinemia. Four types of enzymopenic methemoglobinemia have been described. In addition to methemoglobinemia, individuals with type II, which is the generalized cytochrome b5 reductase deficiency, have severe and progressive neurological disabilities. Here we report a 3-year-old Thai boy with type II hereditary enzymopenic methemoglobinemia. He was born to a second-cousin couple. His central cyanosis was first observed around 10 months of age. His neurological abnormalities were seizures beginning at 1 year of age, microcephaly, and inability to hold his head up. His cardiovascular and pulmonary evaluations were unremarkable. Methemoglobin level by spectral absorption pattern was 18 per cent. A qualitative enzymatic assay confirmed the deficiency of the cytochrome b5 reductase enzyme. With this definite diagnosis, a prenatal diagnosis for the next child of this couple will be possible.

Protective efficacy of a recombinant DNA hepatitis B vaccine in neonates of HBe antigen-positive mothers.

We have assessed the protective efficacy of a recombinant DNA hepatitis B vaccine alone in infants of women who were positive for the surface antigen and the e antigen. The infants received a 10-micrograms dose of the vaccine within 12 hours of birth and additional doses 1, 2, and 12 months later. No significant adverse reactions to vaccination were observed and the vaccine was highly immunogenic. Only 2 (3.6%) of the 55 infants followed up to 13 months became chronically infected with the hepatitis B virus, as evidenced by the persistent presence of hepatitis B surface antigen in serum samples. Without immunoprophylaxis, 65% to 90% of such infants would become chronic carriers. Immunization with a recombinant vaccine without concomitant administration of hepatitis B immunoglobulin, therefore, considerably decreased the incidence of the carrier state.

Comparison of a recombinant DNA hepatitis B vaccine alone or in combination with hepatitis B immune globulin for the prevention of perinatal acquisition of hepatitis B carriage.

The protective efficacy of a recombinant DNA yeast-derived hepatitis B vaccine was assessed alone or in combination with hepatitis B immune globulin (HBIg) in neonates born to surface antigen (HBsAg)-positive and e antigen (HBeAg)-positive mothers. Neonates received either a 10 micrograms dose of vaccine alone or the same dose of vaccine plus 0.5 ml HBIg within 12 h of birth. All infants subsequently received 10 micrograms of vaccine at 1, 2 and 12 months. Only two of the 58 (3.4%) newborns of HBsAg-positive/HBeAg-positive mothers receiving vaccine alone became chronically infected with hepatitis B virus (HBV) while all infants administered vaccine + HBIg were protected. These results indicate that although the administration of HBIg can increase the protection rate, the use of vaccine without concomitant administration of HBIg according to the above schedule could considerably reduce the risk of perinatal HBV transmission.