Pediatric complicated pneumonia and pneumococcal serotype replacement: trends in hospitalized children pre and post introduction of routine vaccination with Pneumococcal Conjugate Vaccine (PCV7)

Recent studies have described an increase in the incidence of complicated pneumonia in children, primarily caused by Streptococcus pneumoniae. The objective of this study was to determine if the incidence of complicated pneumonias in total and due to different pneumococcal serotypes has changed following the introduction of routine immunization with heptavalent pneumococcal conjugate vaccine (PCV7). A retrospective review of patients admitted to the Stollery Children's Hospital in Edmonton, Alberta with complicated pneumonia between July 1, 1997 and June 30, 2007 (5 years before and after the introduction of PCV7) was completed. There were 34 children in the pre- and 68 in the post-PCV7 era (14.31 and 19.91 per 10,000 discharges, respectively, p = 0.114). Patient characteristics were not significantly different, and pneumococcus was the most common organism isolated (pre: 21% (7/34); post: 26% (18/68), p = 0.515). In patients where serotype data was available, non-vaccine pneumococcal serotypes accounted for 67% (12/18) cases in the post-PVC7 era versus 14% (1/7) in the pre-PCV7 era (p = 0.031). The incidence of non-vaccine serotypes was 0.42 and 3.51 per 10,000 discharges in the pre- and post-PCV7 eras, respectively (p = 0.020). There has been a non-significant trend towards an increase in the incidence of complicated pneumonia following the introduction of PCV7. S. pneumoniae remains the predominant organism identified with non-vaccine serotypes now accounting for almost all cases. Although it is not clear if this increase is attributable to the use of PCV7, expanding pneumococcal serotype coverage has the potential to prevent complicated pneumonia.