Estimating vaccine effectiveness against severe influenza in England and Scotland 2011/2012: Applying the screening method to data from intensive care surveillance systems

Helen Thomas*, Nicholas Andrews, Helen Green, N. L. Boddington, Hongxin Zhao, A. Reynolds, J. McMenamin, Richard Pebody

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    12 Citations (Scopus)

    Abstract

    SUMMARY Methods for estimating vaccine effectiveness (VE) against severe influenza are not well established. We used the screening method to estimate VE against influenza resulting in intensive care unit (ICU) admission in England and Scotland in 2011/2012. We extracted data on confirmed influenza ICU cases from severe influenza surveillance systems, and obtained their 2011/2012 trivalent influenza vaccine (TIV) status from primary care. We compared case vaccine uptake with population vaccine uptake obtained from routine monitoring systems, adjusting for age group, specific risk group, region and week. Of 60 influenza ICU cases reported, vaccination status was available for 56 (93%). Adjusted VE against ICU admission for those aged ≥65 years was -10% [95% confidence interval (CI) -207 to 60], consistent with evidence of poor protection from the 2011/2012 TIV in 2011/2012. Adjusted VE for those aged <65 years in risk groups was -296% (95% CI -930 to -52), suggesting significant residual confounding using the screening method in those subject to selective vaccination.

    Original languageEnglish
    Pages (from-to)126-133
    Number of pages8
    JournalEpidemiology and Infection
    Volume142
    Issue number1
    DOIs
    Publication statusPublished - Jan 2014

    Keywords

    • Immunization (vaccination)
    • Influenza
    • Influenza vaccines

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