All-cause pneumonia in children after the introduction of pneumococcal vaccines in the United Kingdom: a population-based study

Methods: We carried out a population-based study to assess the trend of all-cause pneumonia in children aged <10 years between 2002 and 2012. Data were obtained from the IMS Disease Analyzer, a primary care database in UK. Three time-periods were defined to estimate monthly incidence: pre-PCV7 (January 2002–August 2006), post-PCV7 (September 2006–March 2010), and post-PCV13 (April 2010–December 2012). Interrupted time series analysis (ITS) was performed to assess any immediate change or gradual change in the monthly incidence of pneumonia between pre- and post-vaccination introduction. Results: A total of 4,228 children with at least one all-cause pneumonia episode were identified. The overall annual incidence rate of all-cause pneumonia declined by 37% from 3.8 episodes/1,000 person-years in 2002 to 2.4 episodes/1,000 person-years in 2012. Results of ITS analyses indicated that the incidence did not decline immediately after the introduction of PCV7 and PCV13. The incidence declined gradually in children aged <2 years (IRR=0.98; 95%CI=0.97-0.99) post-PCV7, and levelled off during post-PCV13 (IRR=1.00; 95%CI=0.99-1.02). No significant changes in incidence trend was observed in children aged 2-4 years (IRR=0.86; 95%CI=0.68-1.07) and 5-9 years (IRR=0.92; 95%CI=0.73-1.15) after PCV13 introduction. Conclusions: In the UK, the incidence of all-cause pneumonia in children