Empyema hospitalizations increased in US children despite pneumococcal conjugate vaccine.

OBJECTIVE To determine if the incidence of empyema among children in the United States has changed since the introduction of the pneumococcal conjugate vaccine in 2000. METHODS We used the nationally representative Kids' Inpatient Database to estimate the annual total number of hospitalizations of children < or = 18 years of age that were associated with empyema in 1997, 2000,2003, and 2006 [corrected]. Using US Census data, estimated counts were converted into annual incidence rates per 100000 children. Incidence rates were compared between 1997 and later years to determine the impact of pneumococcal conjugate vaccine on hospitalization rates. RESULTS During 2006, an estimated total of 2898 (95% confidence interval [CI]: 2532-3264) hospitalizations of children <or=18 years of age in the United States were associated with empyema. The empyema-associated hospitalization rate was estimated at 3.7 (95% CI: 3.3-4.2) per 100000 children, an increase of almost 70% from the 1997 empyema hospitalization rate of 2.2 (95% CI: 1.9-2.5) per 100000. The rate of complicated pneumonia (empyema, pleural effusion, or bacterial pneumonia requiring a chest tube or decortication) similarly increased 44%, to 5.5 (95% CI: 4.8-6.1) per 100000. The rate of bacterial pneumonia decreased 13%, to 244.3 (95% CI: 231.1-257.5) per 100000. The rate of invasive pneumococcal disease (pneumonia, sepsis, or meningitis caused by Streptococcus pneumoniae) decreased 50%, to 6.3 (95% CI: 5.7-6.9) per 100000. CONCLUSIONS Among children <or=18 years of age, the annual empyema-associated hospitalization rates increased almost 70% between 1997 and 2006, despite decreases in the bacterial pneumonia and invasive pneumococcal disease rates. Pneumococcal conjugate vaccine is not decreasing the incidence of empyema.