1918. Preliminary End-of-Season Estimates of 2014/15 Influenza Vaccine Effectiveness in Preventing Laboratory-Confirmed Influenza-Related Hospitalization from the Serious Outcomes Surveillance (SOS) Network of the Canadian Immunization Research Network (CIRN)
Session: Poster Abstract Session: Vaccines: Influenza
Saturday, October 10, 2015
Room: Poster Hall
Posters
  • McNeil_SOS_Influenza_VE_IDWeek_2015_FINAL[3].pdf (420.4 kB)
  • Background: Canada’s 2014/15 influenza season was characterized by early, intense influenza A(H3N2) activity followed by a smaller influenza B peak. Characterization of circulating viruses demonstrated poor match with the A(H3N2) component of the 2014/15 vaccine suggesting vaccine effectiveness (VE) would be suboptimal. We provide end-of-season estimates of influenza VE for prevention of influenza-related hospitalization in adults.

    Methods: The SOS Network conducted active surveillance for influenza in hospitalized adults from 15Nov14 to 30Apr15 in 16 hospitals. A nasopharyngeal swab for influenza PCR was obtained from all adult patients admitted with acute respiratory illness. Cases were PCR-positive; those influenza-PCR negative  within 7 days of symptom onset with known influenza vaccination status were controls. Crude VE estimates were adjusted using multivariable logistic regression with stepwise backward selection of covariates with a p-value of <0.1 in the univariate analysis.  VE was estimated as (1-OR) X 100.

    Results: 1693 cases and 1936 controls were enrolled; cases were older (mean age 76.1 vs 72.6y; p<.0001); 62.4% cases were >75y. Cases were more likely than controls to have received antivirals (AV) before admission (0.6% vs 0.1%; p=.009) and to be pregnant (1.3% vs 0.2%; p<.0005). 68.2% cases and 69.6% controls had received influenza vaccine ≥ 2 wks prior to symptom onset. Among all age groups, VE was -0.4% (95%CI -24.5, 19.0%) against all strains, -32.7% (-91.2, 7.9%) against A(H3N2) and 20.1% (-15.9, 44.9%) against influenza B. Age, prior receipt of AV, BMI and ≥1 comorbidity were adjusted in the final regression model. In ≥ 65y, VE was -0.9% (-29.6, 21.4%) against all strains, -36.2% (-105.9, 9.9%) against A(H3N2) and 17.8% (-28.7, 47.5%) against B.

    Conclusion: The 2014/15 season in Canada was dominated by circulation of a drifted influenza A(H3N2). While VE cannot be predicted directly from virologic surveillance, mismatch between the circulating strain and vaccine strain this season did result in failure of the vaccine to provide protection against influenza-associated hospitalization. Influenza programs should ensure real-time VE assessment to inform adjunctive public health strategies to minimize influenza disease burden.

    Shelly Mcneil, MD, FRCPC, FIDSA1, Ardith Ambrose, RN1, Melissa K Andrew, MD, PhD1, Guy Boivin, MD2, William Bowie, MD, FRCPC, FIDSA3, Gael Dos Santos, PhD4, May Elsherif, MD1, Karen Green, MSc5, Francois Haguinet, PhD6, Todd Hatchette, MD1, Kevin Katz, MD, CM, MSc, FRCPC7, Jason Leblanc, PhD1, Mark Loeb, MD, MSc, FSHEA8, Donna Mackinnon-Cameron, MMath1, Anne E. Mccarthy, MD9, Janet E. Mcelhaney, MD10, Allison Mcgeer, MD, MSc, FRCPC, FSHEA5, Jeff Powis, MD, MSc, FRCPC11, David Richardson, MD12, Makeda Semret, MD13, Rohita Sharma, PhD14, Vivek Shinde, MD, MPH15, Daniel Smyth, MD, FRCPC16, Sylvie Trottier, MD17, Louis Valiquette, MD, MSc18, Duncan Webster, MD19, Lingyun Ye, PhD1 and Serious Outcomes Surveillance Network of the Canadian Immunization Research Network, (1)Canadian Center for Vaccinology, IWK Health Centre and Nova Scotia Health Authority, Dalhousie University, Halifax, NS, Canada, (2)Centre Hospitalier Universitaire de Québec, Quebec, QC, Canada, (3)University of British Columbia, Vancouver, BC, Canada, (4)Business & Decision Life Sciences (on behalf of GSK Vaccines), Wavre, Belgium, (5)Mount Sinai Hospital, Toronto, ON, Canada, (6)GSK Vaccines, Wavre, Belgium, (7)North York General Hospital, Toronto, ON, Canada, (8)McMaster University, Hamilton, ON, Canada, (9)The Ottawa Hospital, Ottawa, ON, Canada, (10)Advanced Medical Research Institute of Canada, Sudbury, ON, Canada, (11)Toronto East General Hospital, Toronto, ON, Canada, (12)William Osler Health System, Brampton, ON, Canada, (13)McGill University, Montreal, QC, Canada, (14)GSK Vaccines, Mississauga, ON, Canada, (15)GSK Vaccines, King of Prussia, PA, (16)The Moncton Hospital, Moncton, NB, Canada, (17)Centre Hospitalier Universitaire de Quebec, Quebec, QC, Canada, (18)Microbiology and Infectious Diseases, Universite de Sherbrooke, Sherbrooke, QC, Canada, (19)Horizon Health, St. John, NB, Canada

    Disclosures:

    S. Mcneil, GlaxoSmithKline: Grant Investigator and Investigator , Research grant

    A. Ambrose, None

    M. K. Andrew, GlaxoSmithKline: Grant Investigator , Research grant

    G. Boivin, None

    W. Bowie, None

    G. Dos Santos, GSK Vaccines: Consultant , Salary

    M. Elsherif, None

    K. Green, None

    F. Haguinet, GSK Vaccines: Employee , Salary

    T. Hatchette, GlaxoSmithKline: Grant Investigator , Research grant

    K. Katz, None

    J. Leblanc, GlaxoSmithKline: Grant Investigator , Research grant

    M. Loeb, None

    D. Mackinnon-Cameron, None

    A. E. Mccarthy, None

    J. E. Mcelhaney, Sanofi Pasteur: Independent Contractor , Speaker honorarium

    A. Mcgeer, None

    J. Powis, None

    D. Richardson, None

    M. Semret, None

    R. Sharma, GSK Vaccines: Employee , Salary

    V. Shinde, GSK Vaccines: Employee , Salary

    D. Smyth, None

    S. Trottier, None

    L. Valiquette, Pfizer: Grant Investigator , Research grant
    Merck: Grant Investigator , Research grant
    GSK: Grant Investigator , Research grant

    D. Webster, None

    L. Ye, None

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