Child, Household, and Caregiver Characteristics Associated with Hospitalization for Influenza Among Children 6–59 Months of Age: An Emerging Infections Program Study

Compared with older children and adults, young children, especially those <2 years of age, are at increased risk for influenza-associated complications, including hospitalization.1–6 Characteristics previously identified to increase the risk of severe outcomes from seasonal influenza illness include male gender,4 age <12 months,4 gestational age <37 weeks7 and underlying medical conditions including pulmonary,7,8 neurologic/neuromuscular disease8,9 or cardiac conditions.7–9 Few studies have had sufficient power to assess whether social and economic factors such as daycare attendance, caregiver education level, crowding and poverty increase the risk of severe outcomes. The Emerging Infections Program (EIP)10 of the US Centers for Disease Control and Prevention (CDC) is a collaboration of federal, state and local academic and public health partners that conducts population-based surveillance in 10 states, including surveillance for laboratory-confirmed pediatric influenza hospitalizations. During 2005–2008, the EIP network conducted a case-control study to assess the vaccine effectiveness of trivalent-inactivated vaccine in preventing influenza-associated hospitalizations among young children. In this analysis, we sought to identify child, household and caregiver factors associated with hospitalizations because of laboratory-confirmed influenza among children who are recommended to receive the influenza vaccine (children 6–59 months of age).