The impact of new universal child influenza programs in Australia: Vaccine coverage, effectiveness and disease epidemiology in hospitalised children in 2018

Christopher C Blyth; Allen C Cheng; Nigel W Crawford; Julia E Clark; Jim P Buttery; Helen S Marshall; Joshua R Francis; Jocelynne McRae; Tom Kotsimbos; Paul M Kelly; Kristine K Macartney; Paediatric Active Enhanced Disease Surveillance (PAEDS), Influenza Complications Alert Network (FluCAN) Collaboration

doi:10.1016/j.vaccine.2020.02.031

The impact of new universal child influenza programs in Australia: Vaccine coverage, effectiveness and disease epidemiology in hospitalised children in 2018

Vaccine. 2020 Mar 17;38(13):2779-2787. doi: 10.1016/j.vaccine.2020.02.031. Epub 2020 Feb 24.

Affiliations

¹ School of Medicine, University of Western Australia, Perth, WA, Australia; Department of Infectious Diseases, Perth Children's Hospital, Perth, WA, Australia; Department of Microbiology, PathWest Laboratory Medicine WA, QEII Medical Centre, Perth, WA, Australia; Wesfarmers Centre of Vaccines and Infectious Diseases, Telethon Kids Institute, University of Western Australia, Perth, WA, Australia. Electronic address: christopher.blyth@uwa.edu.au.
² Infection Prevention and Healthcare Epidemiology Unit, Alfred Health, Melbourne, Victoria, Australia; School of Public Health and Preventive Medicine, Monash University, Melbourne, Victoria, Australia.
³ Department of General Paediatrics, Royal Children's Hospital, Melbourne, Victoria, Australia; Infection and Immunity, Murdoch Children's Research Institute and University of Melbourne, Victoria, Australia.
⁴ Infection Management and Prevention Service, Queensland Children's Hospital, Brisbane, Queensland, Australia.
⁵ Department of Infection and Immunity, Monash Children's Hospital, Monash Health, Melbourne, Victoria, Australia; Monash Centre of Health Care Research and Implementation, Departments of Paediatrics, Monash University, Melbourne, Victoria, Australia.
⁶ Women's and Children's Health Network, Robinson Research Institute and Adelaide Medical School, The University of Adelaide, Adelaide, SA, Australia.
⁷ Royal Darwin Hospital and Menzies School of Health Research, Charles Darwin University, Darwin, Northern Territory, Australia.
⁸ National Centre for Immunisation Research and Surveillance of Vaccine Preventable Diseases, University of Sydney, Sydney, NSW, Australia; School of Paediatrics and Child Health, University of Sydney, Sydney, NSW, Australia.
⁹ Department of Allergy, Immunology and Respiratory Medicine Alfred Health, Monash University, Victoria, Australia.
¹⁰ ACT Government Health Directorate, Australian National University Medical School, Australian Capital Territory, Australia.
¹¹ National Centre for Immunisation Research and Surveillance of Vaccine Preventable Diseases, University of Sydney, Sydney, NSW, Australia; School of Paediatrics and Child Health, University of Sydney, Sydney, NSW, Australia; Department of Infectious Diseases and Microbiology, Children's Hospital Westmead, Westmead, Sydney, NSW, Australia.

PMID: 32107062
DOI: 10.1016/j.vaccine.2020.02.031

Abstract

Background: New jurisdictionally-based vaccination programs were established providing free quadrivalent influenza vaccine (QIV) for preschool Australian children in 2018. This was in addition to the National Immunisation Program (NIP) funded QIV for Indigenous children and children with comorbid medical conditions. We assessed the impact of this policy change on influenza disease burden and vaccine coverage, as well as report on 2018 vaccine effectiveness in a hospital-based surveillance system.

Methods: Subjects were recruited prospectively from twelve PAEDS-FluCAN sentinel hospital sites (April until October 2018). Children aged ≤16 years hospitalised with an acute respiratory illness (ARI) and laboratory-confirmed influenza were considered cases. Hospitalised children with ARI who tested negative for influenza were considered controls. VE estimates were calculated from the adjusted odds ratio of vaccination in cases and controls.

Results: A total of 458 children were hospitalised with influenza: 31.7% were <2 years, 5.0% were Indigenous, and 40.6% had medical comorbidities predisposing to severe influenza. Influenza A was detected in 90.6% of children (A/H1N1: 38.0%; A/H3N2: 3.1%; A/unsubtyped 48.6%). The median length of stay was 2 days (IQR: 1,3) and 8.1% were admitted to ICU. Oseltamivir use was infrequent (16.6%). Two in-hospital deaths occurred (0.45%). 12.0% of influenza cases were vaccinated compared with 36.0% of test-negative controls. Vaccine effectiveness of QIV for preventing influenza hospitalisation was estimated at 78.8% (95%CI: 66.9; 86.4).

Conclusions: Compared with 2017 (n = 1268 cases), a significant reduction in severe influenza was observed in Australian children, possibly contributed to by improved vaccine coverage and high vaccine effectiveness. Despite introduction of jurisdictionally-funded preschool programs and NIP-funded vaccine for children with risk factors for severe disease, improved coverage is required to ensure adequate protection against paediatric influenza morbidity and mortality.

Keywords: Children; Hospitalization; Influenza; Vaccination; Vaccine effectiveness.

MeSH terms

Adolescent
Australia / epidemiology
Child
Child, Hospitalized
Child, Preschool
Hospitalization
Humans
Immunization Programs*
Infant
Infant, Newborn
Influenza A Virus, H1N1 Subtype
Influenza A Virus, H3N2 Subtype
Influenza Vaccines / administration & dosage*
Influenza, Human* / epidemiology
Influenza, Human* / prevention & control
Sentinel Surveillance
Vaccination Coverage / statistics & numerical data*

Substances

Influenza Vaccines