Open AccessInfluenza hospitalizations in Australian children 2010–2019: The impact of medical comorbidities on outcomes, vaccine coverage, and effectiveness
Author(s) -
Norman Daniel A.,
Cheng Allen C.,
Macartney Kristine K.,
Moore Hannah C.,
Danchin Margie,
Seale Holly,
McRae Jocelynne,
Clark Julia E.,
Marshall Helen S.,
Buttery Jim,
Francis Joshua R.,
Crawford Nigel W.,
Blyth Christopher C.
Publication year - 2022
Publication title -
influenza and other respiratory viruses
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.743
H-Index - 57
eISSN - 1750-2659
pISSN - 1750-2640
DOI - 10.1111/irv.12939
Subject(s) - medicine , vaccination , influenza vaccine , confidence interval , incidence (geometry) , comorbidity , odds ratio , pediatrics , psychological intervention , emergency medicine , intensive care medicine , immunology , physics , psychiatry , optics
Background Children with comorbidities are at greater risk of severe influenza outcomes compared with healthy children. In Australia, influenza vaccination was funded for those with comorbidities from 2010 and all children aged <5 years from 2018. Influenza vaccine coverage remains inadequate in children with and without comorbidities. Methods Children ≤16 years admitted with acute respiratory illness and tested for influenza at sentinel hospitals were evaluated (2010–2019). Multivariable regression was used to identify predictors of severe outcomes. Vaccine effectiveness was estimated using the modified incidence density test‐negative design. Results Overall, 6057 influenza‐confirmed hospitalized cases and 3974 test‐negative controls were included. Influenza A was the predominant type (68.7%). Comorbidities were present in 40.8% of cases. Children with comorbidities were at increased odds of ICU admission, respiratory support, longer hospitalizations, and mortality. Specific comorbidities including neurological and cardiac conditions increasingly predisposed children to severe outcomes. Influenza vaccine coverage in influenza negative children with and without comorbidities was low (33.5% and 17.9%, respectively). Coverage improved following introduction of universal influenza vaccine programs for children <5 years. Similar vaccine effectiveness was demonstrated in children with (55% [95% confidence interval (CI): 45; 63%]) and without comorbidities (57% [(95%CI: 44; 67%]). Conclusions Comorbidities were present in 40.8% of influenza‐confirmed admissions and were associated with more severe outcomes. Children with comorbidities were more likely experience severe influenza with ICU admission, mechanical ventilation, and in‐hospital morality. Despite demonstrated vaccine effectiveness in those with and without comorbidities, vaccine coverage was suboptimal. Interventions to increase vaccination are expected to reduce severe influenza outcomes.