910. Influenza Vaccine Effectiveness in the Prevention of Influenza-related Hospitalization in Canadian Adults Over the 2011/12 through 2013/14 Season: A Pooled Analysis from the Serious Outcomes Surveillance (SOS) Network of the Canadian Influenza Research Network (CIRN)
Session: Oral Abstract Session: Pneumonia from Soup to Nuts
Friday, October 28, 2016: 9:45 AM
Room: 288-290
Background: Ongoing assessment of influenza vaccine effectiveness (VE) is critical to inform public health decision making. The CIRN Serious Outcomes Surveillance (SOS) Network provides annual estimates of influenza VE in the prevention of influenza-associated hospitalization in adults. Here we provided pooled VE estimates across 3 influenza seasons.

Methods:  From 2011/12 - 2013/4, the CIRN SOS Network conducted active surveillance for influenza among hospitalized adults from ~1Nov to 30April each season in up to 45 hospitals in 7 provinces. A nasopharyngeal swab for influenza polymerase chain reaction (PCR) was obtained from all patients admitted with any acute respiratory diagnosis or symptom. Cases were PCR-positive for influenza; test-negative controls matched for date & site of enrolment & age of the case (≥ 65y vs <65y) were enrolled for calculation of VE. VE was estimated as (1-odds ratio of influenza in vaccinated vs unvaccinated patients) x 100 for cases & controls enrolled over 3 seasons. VE estimates were adjusted using multivariable logistic regression with stepwise backward selection of covariates with a p-value of <.1 in univariate analysis.

Results:  3394 cases & 4560 controls were enrolled; 2078 (61.2%) cases & 2939 (64.5%) controls were ≥65y. Over 3 seasons, including all age groups, matched, adjusted VE was 41.7% (34.3-48.3%); VE in adults ≥ 65y was 39.3% (29.4- 47.8%) & in adults 16-64y was 48.0% (37.5-56.7%). Including all age groups, VE against influenza A was 44.1% (35.1-51.9%) & against influenza B was 35.3% (20.7-47.3%). In adults ≥ 65y, VE against influenza A/H3N2 & A/H1N1 was 24.2% (3.6-40.4) & 58.7% (39.4-71.9%) respectively. Corresponding estimates in 16-64y were 44.4% (19.0%-61.8%) & 60.8% (45.1%-72%) respectively.

Conclusion:  While effectiveness of influenza vaccines to prevent serious outcomes varies year to year due to factors such as virulence and match between circulating and vaccine strains, here we demonstrate statistically and clinically important benefit of vaccination in adults spanning three seasons with an average overall effectiveness of 42%. The individual and public health benefit of influenza vaccines should not be understated and public messaging should address overall benefits over time while acknowledging year to year variability.

Shelly a Mcneil, MD, FRCPC, FIDSA1, Todd Hatchette, MD1, Melissa K Andrew, MD, PhD1, Ardith Ambrose, RN1, Guy Boivin, MD, MSc2, Francisco Diaz-Mitoma, MD, PhD3, William Bowie, MD, FRCPC, FIDSA4, Ayman Chit, MBiotech, PhD5, Gael Dos Santos, PhD6, May Elsherif, MD1, Karen Green, MSc7, Francois Haguinet, PhD8, Scott a. Halperin, MD1, Barbara Ibarguchi, MSc9, Jennie Johnstone, MD10, Kevin Katz, MD, CM, MSc, FRCPC11, Joanne M. Langley, MD, FRCPC, FSHEA1, Jason Leblanc, PhD1, Philippe Lagace-Wiens, MD12, Bruce Light, MD12, Mark Loeb, MD, MSc10, Donna Mackinnon-Cameron, MMath1, Anne E. Mccarthy, MD13, Janet E. Mcelhaney, MD3, Allison Mcgeer, MD, MSc7, Andre Poirier, MD, MSc14, Jeff Powis, MD, MSc, FRCPC15, David Richardson, MD16, Makeda Semret, MD17, Vivek Shinde, MD, MPH18, Stephanie Smith, MD, MSc19, Daniel Smyth, MD, FRCPC20, Grant Stiver, MD4, Geoff Taylor, MD19, Sylvie Trottier, MD2, Louis Valiquette, MD, MSc21, Duncan Webster, MD22, Lingyun Ye, PhD1 and on behalf of the CIRN SOS Network Investigators and the Toronto Invasive Bacterial Diseases Network (TIBDN) Investigators, (1)Canadian Center for Vaccinology, IWK Health Centre and Nova Scotia Health Authority, Dalhousie University, Halifax, NS, Canada, (2)Centre Hospitalier Universitaire de Quebec, Quebec, QC, Canada, (3)Health Sciences North Research Institute of Canada, Sudbury, ON, Canada, (4)University of British Columbia, Vancouver, BC, Canada, (5)Leslie Dan Faculty of Pharmacy, Toronto, ON, Canada, (6)Business & Decision Life Sciences (on behalf of GSK Vaccines), Wavre, Belgium, (7)Mount Sinai Hospital, Toronto, ON, Canada, (8)GSK Vaccines, Wavre, Belgium, (9)GSK Vaccines (Current affiliation Bayer Inc.), Mississauga, ON, Canada, (10)McMaster University, Hamilton, ON, Canada, (11)North York General Hospital, Toronto, ON, Canada, (12)St. Boniface Hospital, Winnipeg, MB, Canada, (13)The Ottawa Hospital, Ottawa, ON, Canada, (14)Centre integre de sante et de services sociaux de la Maurice centre du Quebec, Trois-Rivieres, QC, Canada, (15)Toronto East General Hospital, Toronto, ON, Canada, (16)William Osler Health Centre, Brampton, ON, Canada, (17)McGill University, Montreal, QC, Canada, (18)GSK Vaccines (Current affiliation Novavax Vaccines, Washington, DC, USA), King of Prussia, PA, (19)University of Alberta Hospital, Edmonton, AB, Canada, (20)The Moncton Hospital, Moncton, NB, Canada, (21)Universite de Sherbrooke, Sherbrooke, QC, Canada, (22)Horizon Health, St. John, NB, Canada

Disclosures:

S. A. Mcneil, GSK: Grant Investigator , Research grant and Research support
Pfizer: Grant Investigator , Consulting fee , Research grant , Research support and Speaker honorarium
Merck: Consultant and Investigator , Consulting fee , Research support and Speaker honorarium

T. Hatchette, GSK: Investigator , Research grant

M. K. Andrew, GSK: Investigator , Research support

A. Ambrose, None

G. Boivin, Biocryst: Investigator , Research grant
Merck: Investigator , Research grant

F. Diaz-Mitoma, None

W. Bowie, GSK: Investigator , Research grant

A. Chit, Sanofi Pasteur: Employee , Salary

G. Dos Santos, Business and Decision Life Sciences: Consultant , Salary

M. Elsherif, None

K. Green, None

F. Haguinet, GSK Vaccines: Employee , Salary

S. A. Halperin, GSK: Consultant , Grant Investigator and Research Contractor , Consulting fee and Grant recipient

B. Ibarguchi, GSK: Employee , Salary

J. Johnstone, None

K. Katz, None

J. M. Langley, GSK: Investigator , Research grant
Sanofi Pasteur: Investigator , Research grant
PREVENT: Investigator , Research grant

J. Leblanc, None

P. Lagace-Wiens, Merck: Scientific Advisor , Consulting fee and Speaker honorarium

B. Light, None

M. Loeb, GSK: Investigator , Research support

D. Mackinnon-Cameron, None

A. E. Mccarthy, GSK: Investigator , Research support

J. E. Mcelhaney, GSK: Scientific Advisor , Research support and Speaker honorarium
Sanofi Pasteur: Scientific Advisor , Speaker honorarium

A. Mcgeer, GSK: Grant Investigator , Investigator and Scientific Advisor , Research support and Speaker honorarium
Sanofi Pasteur: Grant Investigator , Investigator and Scientific Advisor , Research support and Speaker honorarium
Merck: Grant Investigator , Investigator and Scientific Advisor , Research support and Speaker honorarium

A. Poirier, Actelion: Investigator , Research grant
Genetech: Investigator , Research grant
Sanofi Pasteur: Investigator , Research grant
Vertex: Investigator , Research grant

J. Powis, GSK: Investigator , Research support

D. Richardson, None

M. Semret, None

V. Shinde, GSK: Employee , Salary

S. Smith, None

D. Smyth, None

G. Stiver, None

G. Taylor, None

S. Trottier, None

L. Valiquette, None

D. Webster, None

L. Ye, None

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