Pneumonia and influenza hospitalizations among children under 5 years of age in Suzhou, China, 2005-2011

Background: The disease burden of influenza among children in China has not been well described. Objective: To estimate the influenza-associated excess hospitalization rate and compare the hospitalization length and costs between pneumonia and influenza (P&I) and other community-acquired diseases (CAD) in Suzhou, China. Methods: We retrospectively collected hospital discharge data on pediatric patients' discharge diagnosis, hospital costs, and length of hospital stay in Suzhou. P&I hospitalization was defined as a primary discharge diagnosis of pneumonia and influenza disease (ICD-10 codes J09-J18). Other CAD were common community-acquired diseases among children. Negative binomial regression models were used to estimate the weekly P&I hospitalizations in Suzhou. Excess P&I hospitalizations due to influenza were calculated as the difference in P&I hospitalizations between the epidemic period and the baseline period. Baseline was defined as when the influenza-positive rates were <5% for two consecutive weeks. Results: From October 2005 to September 2011, we identified a total of 180 091 all-cause hospitalizations among children <5 years of age in Suzhou City. The rates of P&I and influenza-associated excess hospitalizations were highest in the 2009-2010 pandemic and 2010-2011 post-pandemic seasons. Infants <6 months of age had the highest P&I hospitalization rates, the longest hospital stays (7.5-8.0 days), and the highest hospitalization costs for P&I. Compared with other CAD, children admitted for P&I had longer hospital stays and higher hospitalization costs. Conclusions: The influenza-associated P&I hospitalization rates and economic burden were high among children. Targeted influenza prevention and control strategies for young children in Suzhou may reduce the influenza-associated hospitalizations in this age group.