Safety, Tolerability, and Immunogenicity of Concurrent Administration of Haemophilus influenzae Type b Conjugate Vaccine (Meningococcal Protein Conjugate) With Either Measles-Mumps-Rubella Vaccine or Diphtheria-Tetanus-Pertussis and Oral Poliovirus Vaccines in 14-to 23-Month-Old Infants
In 1985, the first capsular polysaccharide (polyribosylribitol-phosphate [PRP]) vaccine for Haemophilus influenzae type b was licensed and recommended for routine use in children between 24 and 60 months of age.1,2 In the United States, approximately 75% to 90% of invasive disease due to H influenzae type b occurs in infants younger than 24 months,1,3 a population for whom H influenzae type b polysaccharide vaccine is inadequately immunogenic and protective. In an effort to enhance the immunogenicity of H influenzae type b polysaccharide vaccine for children in the most susceptible age groups, conjugate vaccines have been developed in which the capsular PRP of H influenzae type b has been bound to a variety of carrier proteins, thereby conferring the vaccines with thymic-dependent attributes.4,5 One such conjugate vaccine, in which the carrier protein is diphtheria toxoid (PRP-D), was licensed in 1987 and has been recommended since 1988 for routine use in children 18 months of age and older.6,7 A second conjugate vaccine, in which an oligosaccharide derivative of H influenzae type b capsular PRP is coupled to CRM197, a nontoxic mutant diphtheria toxin (oligo-CRM), was licensed in 1988 and is a sanctioned alternative to PRP-D.8 Another investigational conjugate vaccine, in which the polysaccharide is linked to the outer membrane protein of Neisseria meningitidis group B (PRP-OMPC), has been demonstrated to be both safe and immunogenic when administered in a two-dose schedule to 2- to 6-month-old infants.9 However, anti-PRP antibody levels decline significantly during the ensuing 10 to 15 months10,11; they rise significantly in response to booster doses of either PRP or PRP-OMPC administered 10 to 15 months after the initial priming doses of PRP-OMPC.11,12