Immunogenicity of failed hexavalent vaccines may persist in children

Zanetti AR. Lancet. 2010.doi:10.1016/S1473-3099(10)70195-X.

Two hexavalent vaccines — which combine diphtheria-tetanus-acellular pertussis, hepatitis B virus, inactivated poliovirus and Hemophilus influenzae type b vaccines — maintained immunogenicity for 5 years against hepatitis B virus in children with anti-HBV concentrations lower than 10 mIU/mL, according to recent study results.

The open-label, randomized, controlled study was conducted in six units of the Bambino Gesù Pediatric Research Hospital in Italy. The researchers measured antibody concentrations in 1,543 children 5 years after initial immunization with Hexavac (Sanofi-Aventis) or Infanrix Hexa (GlaxoSmithKline).

Eligible children had antibodies to HBV surface antigen of less than 10 mIU/mL. They were randomly assigned to receive a booster of the recombinant HBV vaccine HBVaxPro (Sanofi-Pasteur) or Energix B monovalent HBV vaccine (GlaxoSmithKline) and then tested 2 weeks later.

Primary outcome measures included the proportion of children with antibodies to HBV surface antigen of at least 10 mIU/mL, geometric mean concentrations of antibody 5 years after immunization and the proportion of children with antibodies less than 10 mIU/mL who had an anamnestic response to the booster, according to the results.

There were 831 children in the Hexavac arm and 709 children in the Infanrix Hexa arm involved in the final analysis.

Antibodies of at least 10 mIU/mL were observed in 38.4% (95% CI, 35.1-41.7) of children in the Hexavac arm and 83.2% (95% CI, 80.5-86.0) of children in the Infanrix Hexa arm (P<.0001).

The average geometric mean concentrations before the booster were 4.5 mIU/mL in the Hexavac group compared with 61.3 mIU/mL in the Infanrix Hexa group (P<.0001 for comparison). After booster, the concentrations were 448.7 mIU/mL in the Hexavac group and 484.9 mIU/mL in the Infanrix Hexa group (P=.60). Also after the booster, HBV antigen concentrations of at least 10 mIU/mL were observed in 92.1% (95% CI, 89.6-94.6) of 444 children in the Hexavac booster arm and in 94.3% (95% CI, 89.8-98.7) of 105 children in the Infanrix Hexa booster arm (P=.40).

Adverse event profiles were similar in the two groups, and no serious adverse events were reported.

Both vaccines were licensed in Europe in 2000. The license for Hexavac was suspended in 2005 due to doubts about the immunogenicity of the HBV component.

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