title: Study of booster doses of two Haemophilus influenzae type b conjugate vaccines including their interchangeability.
abstract: A prospective, two center study of 319 children was undertaken to assess responses to booster immunization in healthy 18-month-olds who completed primary immunization 12 months earlier with Haemophilus influenzae type b (Hib) conjugate vaccine (either HbOC or PRP-T). Interchangeability of these products as boosters was also assessed, using combination products containing diphtheria, pertussis and tetanus components. The study was randomized and evaluator blinded. Sera obtained prior to booster vaccination and 4 weeks later were tested for anti-PRP using an IgG-specific enzyme immunoassay. Pre-immunization anti-PRP levels were low: unmeasurable levels (< 0.06 microgram ml-1) were present in 47% of those primed with HbOC and 35% of those primed with PRP-T (P < 0.05). Most children responded strongly to booster vaccination. Interchanging the products had no detrimental effect. Children who lacked measurable antibody prior to re-vaccination had significantly weaker responses 4 weeks afterward. Earlier Hib booster vaccination should be considered in Canada to avoid low anti-PRP trough levels. Extended follow-up of antibody levels and vaccine protective efficacy is also advisable given the observed heterogeneity of responses to booster vaccination.
authors.affiliation: Vaccine Evaluation Center, BC's Children's Hospital, Vancouver, Canada.
authors.forename: D
authors.initials: D
authors.lastname: Scheifele
authors.forename: B
authors.initials: B
authors.lastname: Law
authors.forename: L
authors.initials: L
authors.lastname: Mitchell
authors.forename: J
authors.initials: J
authors.lastname: Ochnio
mesh_terms: D000906:Antibodies / Q000097:blood*; D001426:Bacterial Proteins / Q000008:administration & dosage* / Q000009:adverse effects / Q000276:immunology; D004890:Erythema / Q000209:etiology; D005260:Female; D006192:Haemophilus Infections / Q000517:prevention & control*; D018073:Haemophilus Vaccines / Q000008:administration & dosage* / Q000009:adverse effects / Q000276:immunology; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood; D007223:Infant; D008297:Male; D011446:Prospective Studies; D013745:Tetanus Toxoid / Q000008:administration & dosage* / Q000009:adverse effects / Q000276:immunology; D018074:Vaccines, Conjugate / Q000008:administration & dosage / Q000009:adverse effects; D014614:Vaccines, Synthetic / Q000008:administration & dosage* / Q000009:adverse effects / Q000276:immunology
chemical_list: D000906:Antibodies; D001426:Bacterial Proteins; D018073:Haemophilus Vaccines; C055753:Haemophilus influenza type b polysaccharide vaccine-tetanus toxin conjugate; D007074:Immunoglobulin G; D013745:Tetanus Toxoid; D018074:Vaccines, Conjugate; D014614:Vaccines, Synthetic; C061963:HibTITER protein, Haemophilus influenzae