title: Influenza vaccine effectiveness for hospital and community patients using control groups with and without non-influenza respiratory viruses detected, Auckland, New Zealand 2014.
abstract: BACKGROUND
  We aimed to estimate the protection afforded by inactivated influenza vaccine, in both community and hospital settings, in a well characterised urban population in Auckland during 2014.
  
  
  METHODS
  We used two different comparison groups, all patients who tested negative for influenza and only those patients who tested negative for influenza and had a non-influenza respiratory virus detected, to calculate the vaccine effectiveness in a test negative study design. Estimates were made separately for general practice outpatient consultations and hospitalised patients, stratified by age group and by influenza type and subtype. Vaccine status was confirmed by electronic record for general practice patients and all respiratory viruses were detected by real time polymerase chain reaction.
  
  
  RESULTS
  1039 hospitalised and 1154 general practice outpatient consultations met all the study inclusion criteria and had a respiratory sample tested for influenza and other respiratory viruses. Compared to general practice patients, hospitalised patients were more likely to be very young or very old, to be Māori or Pacific Islander, to have a low income and to suffer from chronic disease. Vaccine effectiveness (VE) adjusted for age and other participant characteristics using all influenza negative controls was 42% (95% CI: 16 to 60%) for hospitalised and 56% (95% CI: 35 to 70%) for general practice patients. The vaccine appeared to be most effective against the influenza A(H1N1)pdm09 strain with an adjusted VE of 62% (95% CI:38 to 77%) for hospitalised and 59% (95% CI:36 to 74%) for general practice patients, using influenza virus negative controls. Similar results found when patients testing positive for a non-influenza respiratory virus were used as the control group.
  
  
  CONCLUSIONS
  This study contributes to validation of the test negative design and confirms that inactivated influenza vaccines continue to provide modest but significant protection against laboratory-confirmed influenza.
authors.affiliation: The University of Otago, Wellington, PO Box 7343, Wellington South 6242, New Zealand. Electronic address: nevil.pierse@otago.ac.nz.
authors.forename: Nevil
authors.initials: N
authors.lastname: Pierse
authors.affiliation: The Australian National University, Canberra 0200, ACT Australia; Victorian Infectious Diseases Reference Laboratory, Melbourne, VIC, Australia. Electronic address: Heath.Kelly@mh.org.au.
authors.forename: Heath
authors.initials: H
authors.lastname: Kelly
authors.affiliation: Centers for Disease Control and Prevention, Atlanta, GA 30333, USA. Electronic address: isq8@cdc.gov.
authors.forename: Mark G
authors.initials: MG
authors.lastname: Thompson
authors.affiliation: Institute of Environmental Science and Research, Upper Hutt Wellington, New Zealand. Electronic address: Ange.Bissielo@esr.cri.nz.
authors.forename: Ange
authors.initials: A
authors.lastname: Bissielo
authors.affiliation: The University of Auckland, Private Bag 92019, Victoria St West, Auckland, New Zealand. Electronic address: s.radke@auckland.ac.nz.
authors.forename: Sarah
authors.initials: S
authors.lastname: Radke
authors.affiliation: Institute of Environmental Science and Research, Upper Hutt Wellington, New Zealand. Electronic address: sue.huang@esr.cri.nz.
authors.forename: Q Sue
authors.initials: QS
authors.lastname: Huang
authors.affiliation: The University of Otago, Wellington, PO Box 7343, Wellington South 6242, New Zealand. Electronic address: michael.baker@otago.ac.nz.
authors.forename: Michael G
authors.initials: MG
authors.lastname: Baker
authors.affiliation: The University of Auckland, Private Bag 92019, Victoria St West, Auckland, New Zealand. Electronic address: n.turner@auckland.ac.nz.
authors.forename: Nikki
authors.initials: N
authors.lastname: Turner
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D035061:Control Groups; D005260:Female; D058006:General Practice; D006760:Hospitalization; D006801:Humans; D007223:Infant; D007252:Influenza Vaccines / Q000276:immunology / Q000627:therapeutic use*; D007251:Influenza, Human / Q000453:epidemiology / Q000517:prevention & control*; D008297:Male; D008875:Middle Aged; D009520:New Zealand / Q000453:epidemiology; D012140:Respiratory Tract Diseases / Q000453:epidemiology / Q000821:virology; D018571:Sentinel Surveillance; D014611:Vaccination / Q000706:statistics & numerical data*; D015164:Vaccines, Inactivated / Q000276:immunology / Q000627:therapeutic use; D055815:Young Adult
chemical_list: D007252:Influenza Vaccines; D015164:Vaccines, Inactivated
keywords: Immunisation; Influenza vaccine; Test case negative design; Vaccination; Vaccine effectiveness