Background: Each year, millions of children get sick with seasonal flu, thousands of children are hospitalized, and some children die from flu. While the U.S. has a comprehensive influenza surveillance system reporting on current flu activity, and the Centers for Disease Control and Prevention (CDC) publishes weekly updates on their website (FluView), there is a lack of literature analyzing trends among the virus types causing flu and flu-related hospitalizations among children over multiple flu seasons. This study aimed to identify tends over time (2010-2019) in the proportion of children with lab-confirmed flu and hospitalized for flu, along with the proportion of virus types children are infected with.

Methods: A secondary data analysis was conducted using the existing U.S. national influenza surveillance data assembled and provided by the CDC. The study included children in the United States with lab-confirmed flu or with flu-associated hospitalization during the 2010-2011 flu season through the 2018-2019 flu season. Data from hospitalization surveillance and virologic surveillance were analyzed across all 9 flu seasons.

Results: Trends in the proportion of seasonal flu and flu-related hospitalizations among children showed a significant decrease over time (2010-2019). Additionally, trends in the proportion of flu A(H3N2) virus among children showed a significant decrease over time. While this study revealed a strong, positive relationship between the proportion of flu and flu-related hospitalizations among young children (0-4 yr) and older children (5-24 yr), a strong, negative relationship was observed between the proportion of flu and flu-related hospitalizations among children (0-4 yr) and older adults (65+).

Conclusion: A significant decrease in proportion of flu and flu hospitalizations among children was observed over time, revealing a trend of decreased burden of flu among children compared to other age groups. A significant relationship was observed between children and older adults, revealing that as trends of flu among children decreased, trends increased among older adults. Trends in seasonal flu and flu-related complications have important implications for flu prevention and control efforts.