1 INTRODUCTION Influenza is a highly infectious acute viral disease that leads to annual global epidemics. It is estimated that there are more than 109 million cases of influenza episodes among children under 5 years of age worldwide, leading to as many as 34 800 influenza-associated deaths for the same age group.1 Although the percentage of fully vaccinated pediatric individuals in Taiwan can reach up to 74.8%,2 the burden of influenza in this age group remains substantial.
