Pharyngeal colonization with Haemophilus influenzae type b: a longitudinal study of families with a child with meningitis or epiglottitis due to H. influenzae type b.

A longitudinal study of pharyngeal colonization with Haemophilus influenzae type b included 264 members of families that had a child with meningitis or epiglottitis due to this organism. It was found that (1) 52 of 67 such families contained at least one carrier of H. influenzae type b, who was usually a sibling; (2) H. influenzae type b spread slowly in 39 families colonized continuously during a six-month period, with only eight of 19 uncolonized siblings acquiring the organism during that time; (3) 18 of 30 initially colonized families contained one or more carriers after 12 months, including 30% of initially colonized siblings; (4) the highest carrier rate of H. influenzae type b occurred in recovered patients, 80% of whom were colonized after hospital discharge; (5) titers of antibody in serum were higher in colonized than in uncolonized individuals (P less than 0.001); (6) levels of antibody in colonized children were lower in those younger than two years than in older children (P less than 0.001); and (7) prolonged or heavy colonization with H. influenzae type b was not associated with unusually high titers of antibody.