Radiographic pneumonia in young, highly febrile children with leukocytosis before and after universal conjugate pneumococcal vaccination.

OBJECTIVES: Studies before the introduction of conjugate pneumococcal vaccine demonstrated a high rate of radiographic pneumonia among highly febrile young children with leukocytosis and no other identified source of infection. We sought to evaluate the impact of universal vaccination with Prevnar (pneumococcal conjugate vaccine [PCV]) on the incidence and characteristics of occult and nonoccult radiographic pneumonia among these children.
METHODS: Retrospective cohort study of children younger than 5 years seen in an urban pediatric emergency department with temperature 39 degrees C or higher, white blood cell count 20,000/microL or higher, and chest radiograph performed. Pneumonia was defined as focal infiltrate or consolidation on chest radiograph as read by an attending radiologist. Occult pneumonia was defined as radiographic pneumonia in the absence of lower respiratory tract signs or cough.
RESULTS: Before universal pneumococcal vaccination, radiographic pneumonia was found in 190 (21%) of 889 (95% confidence interval [CI], 19-24) eligible children compared with 61 (18%) of 335 (95% CI: 14, 23) eligible children after universal vaccination (P = 0.27). Occult pneumonia was identified in 61 (15%) of 404 (95% CI, 12-19) pre-PCV compared with 13 (9%) of 147 (95% CI, 5-15) post-PCV (P = 0.07). In children younger than 2 years, radiographic pneumonia was identified in 121 (17%) of 709 (95% CI, 14-20) pre-PCV and 26 (10%) of 254 (95% CI, 7-15) post-PCV (P = 0.01).
CONCLUSIONS: Clinicians should continue to consider chest radiography in young highly febrile children with leukocytosis and no other identified source of infection.