Risk conditions in children hospitalized with influenza in Norway, 2017–2019

Abstract

Background Norwegian children are more frequently hospitalized with influenza than adults. Little is known about the characteristics of these children. Our aim was to investigate the presence of pre-existing risk conditions and to determine the duration of influenza hospitalizations in children during two influenza seasons. Methods The Norwegian Patient Registry holds data on all hospitalized patients in Norway. We included all patients younger than 18 years hospitalized with a diagnosis of influenza during the influenza seasons 2017–18 and 2018–19. Pre-existing risk conditions for influenza were identified by ICD-10 diagnoses in the Norwegian Patient Registry. In addition, information on asthma diagnoses were also retrieved from the Norwegian Registry for Primary Health Care. To estimate the prevalence of risk conditions in the child population, we obtained diagnoses on all Norwegian children in a two-year period prior to each influenza season. We calculated age-specific rates for hospitalization and risk for being hospitalized with influenza in children with risk conditions. Results In total, 1013 children were hospitalized with influenza during the two influenza seasons. Children younger than 6 months had the highest rate of hospitalization, accounting for 13.5% of all admissions (137 children). Hospitalization rates decreased with increasing age. Among children hospitalized with influenza, 25% had one or more pre-existing risk conditions for severe influenza, compared to 5% in the general population under 18 years. Having one or more risk conditions significantly increased the risk of hospitalization, (Odds Ratio (OR) 6.1, 95% confidence interval (CI) 5.0–7.4 in the 2017–18 season, and OR 6.8, 95% CI 5.4–8.4 in the 2018–19 season). Immunocompromised children and children with epilepsy had the highest risk of hospitalization with influenza, followed by children with heart disease and lung disease. The average length of stay in hospital were 4.6 days, and this did not differ with age. Conclusion Children with pre-existing risk conditions for influenza had a higher risk of hospitalization for influenza. However, most children (75%) admitted to hospital with influenza in Norway during 2017–2019 did not have pre-existing risk conditions. Influenza vaccination should be promoted in particular for children with risk conditions and pregnant women to protect new-borns.

Hospitalization of Children Aged <5 Years Due to Influenza: Study Based on the National Hospitalization Registry

“…A study based on The Norwegian Patient Registry revealed a decrease in the hospitalization rates among children with influenza the older the children were [ 9 ]. A similar trend was observed in our study.…”

“…In a study based on data from 16 countries, which represented 79% of the population of America, the average pooled rate of influenza-related respiratory hospitalizations in children under 5 years of age amounted to 90 cases per 100,000 population [ 8 ]. A study based on the Norwegian Patient Registry showed the highest hospitalization rates in children aged under 6 months and a drop in the number of hospitalization cases the older the children were [ 9 ]. A systematic review and meta-analysis made in China showed the highest rates of hospitalization related to influenza in the group of children at the age of <5 years, and thus this group was considered to significantly contribute to influenza-related morbidity and mortality burden [ 10 ].…”

“…A systematic review and meta-analysis made in China showed the highest rates of hospitalization related to influenza in the group of children at the age of <5 years, and thus this group was considered to significantly contribute to influenza-related morbidity and mortality burden [ 10 ]. It has been revealed in other studies that influenza infection is the cause of a considerable number of hospital admissions among young children [ 9 , 11 , 12 , 13 , 14 , 15 ].…”

Influenza Vaccination in Patients With Congenital Heart Disease in the Pre-COVID-19 Era: Coverage Rate, Patient Characteristics, and Outcomes

“…Indeed, children with heart diseases aged 0-4 years have a 6.2 greater odds, and those aged 5-9 years have a 30.6 greater odds of being hospitalized for influenza. 21 When admitted to the hospital for influenza, such children are at significantly increased risk for in-hospital mortality, acute respiratory failure, acute kidney injury, need for invasive and noninvasive mechanical ventilation, myocarditis, and need for extracorporeal membrane oxygenation. 22 Understandably, this corresponded with a higher length of stay.…”

Correction to: Risk conditions in children hospitalized with influenza in Norway, 2017–2019

“…Following publication of the original article [ 1 ], an error was identified in one author’s affiliations: Dr. Siri Helene is also affiliated to the Department of Biostatistics, Oslo Centre for Biostatistics and Epidemiology, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway.…”