342. Vaccine Effectiveness of the Southern Hemisphere Trivalent Inactivated Vaccine in Healthy Young Children using Test Negative and Other Virus Detected Controls
Session: Poster Abstract Session: Influenza Vaccine in Children and Adults
Thursday, October 3, 2013
Room: The Moscone Center: Poster Hall C
Posters
  • IDWeek poster FINAL uploaded.pdf (242.4 kB)
  • Background: There are few studies evaluating the effectiveness of the Southern Hemisphere trivalent influenza vaccination (TIV) in children or TIV effectiveness in children <2 years. The Western Australian Influenza Vaccine Effectiveness study commenced in 2008 to evaluate a state-based program providing TIV to children aged 6-59 months.

    Methods: An observational study enrolling children presenting to a tertiary paediatric hospital with influenza-like-illness was conducted from 2008-12. Vaccination status was determined by parental questionnaire and confirmed using the national immunisation register and/or vaccine providers. Fully vaccinated was defined as i) two doses of TIV ≥21 days apart and ≥14 days prior to presentation or ii) one dose ≥14 days prior to presentation and two or more doses in a previous year. Nasopharyngeal sampling for respiratory virus PCR and culture was performed. The test-negative design was used to estimate vaccine effectiveness (VE). Fully vaccinated and unvaccinated children were compared using two control groups: influenza test negative subjects (test negative controls) and subjects in whom another virus was detected (other virus detected controls). Adjusted odds ratios were estimated from models with season, week of disease onset, age, sex, Indigeneity, prematurity and comorbidities as covariates. Subjects enrolled in 2009 were excluded from VE calculations. VE was estimated for the influenza season.

    Results: Of 2408 children enrolled (median: 1.9y), 21.0% required hospital admission. Only 15.3% of children had significant comorbidities. Influenza was identified in 469 children (fluA, 13.7%; fluB: 5.8%). Another respiratory virus was identified in 1493 children (62.0%). Overall, 16.6% children were fully vaccinated and 8.4% partially vaccinated. Using test negative controls, VE for children recruited through the emergency department (2008, 2010-2012) was 63.8% (95%CI: 27.4-81.9%). No significant difference in VE was observed with other virus detected controls (68.2%; 95%CI: 26.5-86.2%). The VE for children < 2 years was 87.7% (95%CI: 39.5-97.5%).

    Conclusion: This study demonstrates the effectiveness of the Southern Hemisphere TIV in young children over multiple seasons using both test negative controls and other virus detected controls.  TIV was effective in children aged <2 years.

    Christopher Blyth, MBBS1,2,3,4, Peter Jacoby, MSc5, Paul Effler, MD, MPH6, Heath Kelly, MPH7,8, David Smith, MBBS4, Christine Robins, BSc3, Gabriela Dixon, MBBS3 and Peter Richmond, MBBS1,2,3, (1)School of Paediatrics and Child Health, University of Western Australia, Perth, Australia, (2)Department of Paediatric and Adolescent Medicine, Princess Margaret Hospital for Children, Perth, Australia, (3)Vaccine Trials Group, Telethon Institute of Child Health Research, Perth, Australia, (4)Department of Microbiology, PathWest Laboratory Medicine WA, Perth, Australia, (5)Telethon Institute of Child Health Research, Perth, Australia, (6)Communicable Disease Control Directorate, Perth, Australia, (7)Victorian Infectious Diseases Reference Laboratory, Melbourne, Australia, (8)Australian National University, Canberra, Australia

    Disclosures:

    C. Blyth, None

    P. Jacoby, None

    P. Effler, None

    H. Kelly, None

    D. Smith, None

    C. Robins, None

    G. Dixon, None

    P. Richmond, None

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