The induction of immunologic memory after vaccination with Haemophilus influenzae type b conjugate and acellular pertussis-containing diphtheria, tetanus, and pertussis vaccine combination.

Author(s): Goldblatt D, Richmond P, Millard E, Thornton C, Miller E

Affiliation(s): Immunobiology Unit, Institute of Child Health, London WC1N 1EH, UK. d.goldblatt@ich.ucl.ac.uk

Publication date & source: 1999-08, J Infect Dis., 180(2):538-41.

Publication type: Clinical Trial; Randomized Controlled Trial

The significance of reduced antibody responses to the Haemophilus influenzae type b (Hib) component of acellular pertussis-containing combination vaccines (DTaP-Hib) is unclear. A DTaP-Hib vaccine evaluated in infants vaccinated at ages 2, 3, and 4 months showed reduced anti-Hib polysaccharide IgG (geometric mean concentration [GMC], 1.23 microgram/mL; 57%, >1.0 microgram/mL). Polyribitolribosyl phosphate (PRP) and Hib conjugate (PRP-T) vaccine given as a booster during the second year of life was evaluated for the presence of immunological memory. After boosting, most children achieved anti-PRP IgG >1.0 microgram/mL, although the GMC was higher with PRP-T (88.5 microgram/mL) than with PRP vaccine (7.86 microgram/mL, P<.001). The GMC of the PRP group was higher than anticipated for naive PRP recipients of the same age. PRP-specific IgG avidity was significantly higher after boosting than after priming, providing further evidence for the generation of memory. Despite reduced immunogenicity, DTaP-Hib combination vaccines appear to prime for immunologic memory.