Defining the burden of pneumonia in children preventable by vaccination against Haemophilus influenzae type b

Objectives. To determine the burden of pneumonia requiring hospitalization in infants and young children preventable by vaccination against Haemophilu s influenzae type b (Hib). Design, Vaccination centers in Santiago, Chile, were randomly selected to a dminister PRP-T, an Hib conjugate vaccine, combined with diphtheria-tetanus toxoids-pertussis (DTP) vaccine or DTP alone. Subjects. Infants who received greater than or equal to 2 doses of DTP or D TP and Hib conjugate vaccine combined, Main outcome measures. Pneumonia episodes leading to hospitalization accomp anied by indicators of likely bacterial infection including radiologic evid ence of alveolar consolidation or pleural effusion, an elevated erythrocyte sedimentation rate (greater than or equal to 40 mm/h) or bronchial breath sounds on auscultation, Results, In participants age 4 to 23 months, PRP-T reduced the incidence of pneumonia associated with alveolar consolidation or pleural effusion by 22 % (95% confidence interval, -7 to 43) from 5.0 to 3.9 episodes per 1000 chi ldren per year. When the pneumonia case definition included any of the foll owing, alveolar consolidation, pleural effusion, erythrocyte sedimentation rate greater than or equal to 40 mm/h or bronchial breath sounds, PRP-T pro vided 26% protection (95% confidence interval, 7 to 44) and prevented 2.5 e pisodes per 1000 children per year, Conclusions. Hib vaccine provides substantial protection against nonbactere mic pneumonia, particularly those cases with alveolar consolidation, pleura l effusion or other signs of likely bacterial infection. Hib vaccination pr evented similar to 5 times as many nonbacteremic pneumonia cases in infants as meningitis cases, thus indicating that the largest part of the effect o f Hib vaccination might be undetectable by routine culture methods.