Reduction in the incidence of acute bronchitis by an oral Haemophilus influenzae vaccine in patients with chronic bronchitis in the highlands of Papua New Guinea.

Following the administration of a standardized questionnaire, 62 adult patients with chronic bronchitis were enrolled into a double-blind controlled trial of an oral killed Haemophilus influenzae vaccine in the highlands of Papua New Guinea. A 3-day course of vaccine or placebo was given monthly for 3 consecutive months. Participants were monitored weekly over 12 months for acute exacerbations; early morning sputum specimens were collected monthly and during acute exacerbations. Density of colonization by H. influenzae and H. parainfluenzae was determined by standard quantitative and semiquantitative techniques, and the latter method (quadrant score) was used to determine the density of growth of pneumococci. A total of 30 patients received vaccine and 32 placebo. The incidence rate of acute bronchitis in the vaccine group (0.011 episodes/person-weeks) was significantly lower than that in the placebo group (0.021 episodes/person-weeks), but there was no difference between the two groups in the incidence rates of more severe disease. Vaccine efficacy was maximal at times of peak incidence of disease. There was no evidence of a decline in vaccine efficacy for acute bronchitis over the 12-month follow-up period. The number of viable H. influenzae in the sputum declined in both vaccine and placebo groups over the 12-month follow-up period. The average concentration of H. influenzae in the vaccine group fell below that in the placebo group within 1 to 2 months after first immunization and remained so for 12 months, although the difference between the two groups narrowed during the follow-up period.(ABSTRACT TRUNCATED AT 250 WORDS)