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Influenza vaccine effectiveness in older adults compared with younger adults over five seasons

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  • Influenza vaccine effectiveness in older adults compared with younger adults over five seasons

    Vaccine. 2018 Feb 2. pii: S0264-410X(18)30094-X. doi: 10.1016/j.vaccine.2018.01.045. [Epub ahead of print]
    Influenza vaccine effectiveness in older adults compared with younger adults over five seasons.

    Russell K1, Chung JR2, Monto AS3, Martin ET3, Belongia EA4, McLean HQ4, Gaglani M5, Murthy K5, Zimmerman RK6, Nowalk MP6, Jackson ML7, Jackson LA7, Flannery B2.
    Author information

    Abstract

    BACKGROUND:

    There have been inconsistent reports of decreased vaccine effectiveness (VE) against influenza viruses among older adults (aged ≥ 65 years) compared with younger adults in the United States. A direct comparison of VE over multiple seasons is needed to assess the consistency of these observations.
    METHODS:

    We performed a pooled analysis of VE over 5 seasons among adults aged ≥ 18 years who were systematically enrolled in the U.S. Flu VE Network. Outpatients with medically-attended acute respiratory illness (cough with illness onset ≤ 7 days prior to enrollment) were tested for influenza by reverse transcription polymerase chain reaction. We compared differences in VE and vaccine failures among older adult age group (65-74, ≥75, and ≥ 65 years) to adults aged 18-49 years by influenza type and subtype using interaction terms to test for statistical significance and stratified by prior season vaccination status.
    RESULTS:

    Analysis included 20,022 adults aged ≥ 18 years enrolled during the 2011-12 through 2015-16 influenza seasons; 4,785 (24%) tested positive for influenza. VE among patients aged ≥ 65 years was not significantly lower than VE among patients aged 18-49 years against any subtype with no significant interaction of age and vaccination. VE against A(H3N2) viruses was 14% (95% confidence interval [CI] -14% to 36%) for adults ≥ 65 years and 21% (CI 9-32%) for adults 18-49 years. VE against A(H1N1)pdm09 was 49% (95% CI 22-66%) for adults ≥ 65 years and 48% (95% CI 41-54%) for adults 18-49 years and against B viruses was 62% (95% CI 44-74%) for adults ≥ 65 years and 55% (95% CI 45-63%) for adults 18-49 years. There was no significant interaction of age and vaccination for separate strata of prior vaccination status.
    CONCLUSIONS:

    Over 5 seasons, influenza vaccination provided similar levels of protection among older and younger adults, with lower levels of protection against influenza A(H3N2) in all ages.
    Published by Elsevier Ltd.


    KEYWORDS:

    Human; Influenza; Influenza vaccine effectiveness; Influenza vaccines; Older adults

    PMID: 29402578 DOI: 10.1016/j.vaccine.2018.01.045
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