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Influenza epidemiology among hospitalized children in Stockholm, Sweden 1998-2014
Rutger Bennet1, Johan Hamrin1, Benita Zweygberg Wirgart2
1Astrid Lindgren Children's Hospital, SE-171 76 Stockholm, Sweden.
Insights
Severe influenza hospitalizations in children are common, particularly in infants. The study highlights an increasing trend of influenza B cases, impacting vaccination strategies for pediatric populations.
Area of Science:
- Pediatric infectious diseases
- Epidemiology
- Virology
Background:
- Influenza is a significant cause of pediatric hospitalizations.
- Long-term, population-based studies are needed to understand severe influenza epidemiology in children.
- This study describes the epidemiology of severe influenza in a defined pediatric population from 1998 to 2014.
Purpose of the Study:
- To describe the epidemiology of severe influenza in hospitalized children.
- To analyze trends and characteristics of influenza hospitalizations over a 17-year period.
- To compare different influenza strains (A, B, and A(H1N1)pdm09) regarding comorbidities and complications.
Main Methods:
- Retrospective analysis of annually collected data on virologically confirmed influenza cases in children aged 0-17 years.
- Data collected from a defined catchment area with a population of 230,000 children.
- Information on comorbidities and complications extracted from case records.
Main Results:
- 922 children were hospitalized with influenza; the annual hospitalization rate remained stable (22.5-24.2 per 100,000).
- Major outbreaks included influenza A(H3N2) in 2003-2004 and the A(H1N1) pandemic in 2009-2010.
- Influenza B proportion increased from 8% to 28%; infants (<3 months) had the highest admission rate (169 per 100,000); 34% had comorbidities, 41% had complications, and 11% required intensive care.
Conclusions:
- Influenza remains a critical reason for child hospitalization, especially in the first years of life.
- The rising proportion of influenza B cases necessitates consideration in influenza vaccine recommendations for children.
- Findings underscore the importance of influenza vaccination and monitoring in pediatric populations.
Background:
Influenza remains a common reason for the hospitalization of children. There is a need for long term studies that are also population based. We describe the epidemiology of severe influenza in a defined population 1998-2014.
Method:
Retrospective study of annually collected data of virologically confirmed influenza in hospitalized children 0-17 years living in the catchment area (230,000 children). We gathered information about comorbidity and complications from case records, and compared Influenza A, B and A(H1N1)pdm09 with respect to these factors.
Results:
A total of 922 children with influenza were hospitalized. The mean rate remained unchanged at 22.5-24.2 per 100,000 children per year. There were two major outbreaks: influenza A(H3N2) in 2003-2004 and the A(H1N1) pandemic in 2009-2010. The proportion of children with influenza B increased from 8% during the first half of the study period to 28% during the second half. The highest admission rate was found in children <3 months of age, 169 per 100,000. Children with influenza B were older than those with influenza A. Comorbidity was found in 34%, complications in 41%, and 11% needed intensive care management. The mortality rate was 0.17/100,000 children.
Conclusion:
Influenza remains an important reason for the hospitalization of children, especially during the first years of life. The increasing proportion of influenza B may have to be considered when recommending influenza vaccines.
