Epidemiology of nasopharyngeal colonization with nontypeable haemophilus influenzae in the first 2 years of life

Two hundred children were followed from birth through 2 years of age with nasopharyngeal cultures to determine the normal colonization pattern of nontypeable Haemophilus infiuenzae. Forty-four percent of the children were colonized on one or more occasions; the acquisition rate was greatest in the first year. Monthly prevalence rates were 11%. Colonization with the initial strain persisted 1-5 months (median, 2). Children carried 1 predominant strain at a time but became colonized with up to 7 different strains (mean, 2.2). Children colonized with a single strain for ≤2 months produced a greater nasopharyngeal secretory IgA to nontypeable H. influenzae response than did children colonized with different strains (log 2.35 ± 0.68 vs. 1.89 ± 0.25 U of P6 secretory IgA/ng/mL of total secretory IgA, P <.01). The duration of colonization with a strain and acquisition of a new strain may be affected in part by the local production of specific secretory IgA.