Immunogenicity of low doses of hepatitis B vaccine in children: a study in 650 New Zealand children

Assessment of anti-HBs antigen in 6- to 9-year-old children routinely vaccinated via vaccination program in Iran

OBJECTIVE

To determine persisting antibody levels to hepatitis B virus (HBV) antigen in healthy children, aged 6-9 years, vaccinated at birth.

METHODS

Blood samples were collected from 374 vaccinated children (178 girls and 196 boys) and 57 unvaccinated children, attending Shiraz Primary School, Shiraz, Iran from September 2002 to April 2003. An HBV surface antibody (anti-HBs) was determined using enzyme-linked immunosorbent assay.

RESULTS

The anti-HBs titer was detected in 17% of the 8-year-old children, 7.7% of the 7-year-old children and 46.6% of the 6-year-old children. The decrease was greatest in the 9-year-old children; more than half (54.3%) had a titer of less than 10 IU/ml, indicating a decrease in antibody levels with increasing age/time. Conversely, more than 35% of the 6-year-old children had a titer greater than 150 IU/ml compared with 24, 12 and 7% of children at the age of 7, 8 and 9, respectively, whose antibody titer was less than 150 IU/ml.

CONCLUSION

Antibody titer declined with time. In comparison with other countries, the antibody titer in Iranian children was much lower.

History of hepatitis B vaccination in New Zealand: lessons for Australia?

Recognition of the high prevalence of and the problems caused by the hepatitis B virus (HBV) infection in the North Island of New Zealand is largely due to the observations and work of one man, Alexander Milne. This article outlines the history of the events that led up to the culmination of his team's work--a national hepatitis vaccination strategy for New Zealand children. The situation in Australia is reassessed in the light of the New Zealand example with data based on benefit-cost analysis of various vaccination strategies.

Very low dose hepatitis B vaccination in the newborn: anamnestic response to booster at four years

Seventy-eight children who had received three very low doses (1 or 2 microg) of Merck, Sharp and Dohme (MSD) plasma-derived vaccine (PDV) in early infancy were followed to approximately four years of age. Of the 70 who had responded to the initial course of vaccine with measurable anti-HBs, levels had fallen to below 10 mlU/ml in 38% of subjects given 1 microg doses and in 17% of those who had been given 2 microg doses. None of the children were positive for anti-HBc. Two weeks after 2 microg dose of MSD recombinant DNA (rDNA) vaccine all subjects had more than 10 mlU/ml of anti-HBs, with 90% exceeding 1,000 mlU/ml. A response to hepatitis B vaccine in infancy is followed by an effective immunological memory for several years, even if anti-HBs falls to low levels. The rDNA hepatitis B vaccine (MSD) in 2 microg doses is an effective booster following a primary course of plasma derived vaccine.

Low-dose intradermal vaccination of medical and dental students

In 454 medical and dental students who were vaccinated against hepatitis B by means of a low dose (0.1 mL) of serum-derived vaccine, seroconversion rates of 27%, 70% and 89% were obtained after the first, second and third doses, respectively. These figures are comparable with the results that have been reported for the conventional intramuscular schedule, as were the final antibody titres. A fourth intradermal dose boosted the percentage of students who were protected from 82% to 87%. There was a significant variation in the response to different batches of vaccine. This study shows that the low-dose intradermal method is practicable and effective and can be used to achieve great economy in hepatitis B vaccination programmes. The possibility of adding hepatitis B to the present formula of triple antigen should be investigated as a way of extending hepatitis B vaccination to all infants in our community.

Antibody response after intradermal administration of recombinant hepatitis B vaccine in children

Intradermal vaccination with recombinant hepatitis B vaccine was performed in 33 children (mean age 3.3 years). A 2 micrograms dose was given at 0, 1 and 6 months and antibody responses were determined 20 months after the initial dose. In 32/33 children, serum antibodies to HBs were demonstrated, with a geometric mean level of 26.5 IU/l, and 24 children (73%) had anti-HBs levels greater than or equal to 10 IU/l. The results indicate that intradermal vaccination with recombinant hepatitis B vaccine may be an alternative for vaccination of small children.

Low-dose (2 micrograms) hepatitis B vaccination in medical students: comparable immunogenicity for intramuscular and intradermal routes

In a randomized controlled trial, 165 healthy medical students were immunized either by the intramuscular route (IM group) or by the intradermal route (ID group) with low-dose (2 micrograms) plasma hepatitis B vaccine (HB-VAX) at months 0, 1, 2, and 6. At month 7, protective immunity (anti-HBs greater than 10 IU/l) was observed in 90% (95% confidence interval [Cl]: 84-97) of group IM and in 94% (95% Cl: 89-99) of group ID; also geometric mean titres (IM: 533 IU/l; ID:541 IU/l) were very similar at month 7. Sixty-six (IM: 29; ID: 37) of 107 vaccinees with anti-HBs less than 1,000 IU/l at month 7 received a 2 micrograms booster injection at month 12. Long-term immunity (anti-HBs greater than 1,000 IU/l) was finally observed in 58% for group IM and 66% for group ID. For low-dose hepatitis B immunization, which reduces costs to about 16%, the IM route is to be preferred in young healthy individuals in view of an ease of administration, avoidance of long-term local side effects, and the known protective immunity of intramuscularly induced anti-HBs antibodies.