Objective: To describe clinical characteristics and outcomes of laboratory-confirmed influenza in hospitalized children in a tertiary care center and to identify factors associated with the severity.

Materials and Methods: The present study was a retrospective medical chart review study conducted at King Chulalongkorn Memorial Hospital, Bangkok, Thailand. Data were extracted from children aged under 15 years old hospitalized between January 2014 and December 2018. Patients who had laboratory-confirmed influenza by rapid antigen detection or molecular testing were included. Severe influenza was defined as patients who developed influenza complications or duration of hospitalization for more than three days. Multivariate logistic regression was used to identify the associated factors with the severity of the disease.

Results: Three hundred fifty-seven influenza patients were included with median age of 43 months (IQR 19 to 81), of which 63.3%
were aged under 60 months. There were 174 patients (48.7%) with comorbidities, most common were immunosuppression (18.2%),
chronic pulmonary disease (12.2%), and congenital heart disease (11.5%). Fifty-seven out of 183 patients (31.1%) had history of
influenza vaccination in the medical records. One hundred sixty-one patients (45.1%) had 212 influenza complications including
influenza-related pneumonia (89, 24.9%), secondary bacterial infection (53, 14.8%), and neurologic complications (47, 13.2%), in
which 27 cases (7.6%) were transferred to intensive care unit (ICU). Four cases (1.1%) died but not directly related to influenza.
Associated factors with complicated influenza were aged less than 24 months [aOR 2.67 (95% CI 1.68 to 4.26)] and presence of
chronic lung disease [aOR 4.34 [95% CI 2.01 to 9.35)].

Conclusion: Two-third of the children hospitalized with influenza were younger than 60 months. Nearly half developed complications
most associated with the age of less than two years old and patients with chronic lung disease. Low rates of vaccination were
demonstrated.

Keywords: Influenza, Pediatrics, Complications, Pneumonia, Hospitalization

DOI: doi.org/10.35755/jmedassocthai.2020.11.11257

Received 9 April 2020 | Revised 27 June 2020 | Accepted 3 July 2020