title: Effectiveness of subunit influenza vaccination in the 2014-2015 season and residual effect of split vaccination in previous seasons.
abstract: BACKGROUND
  In Navarra, Spain, subunit vaccine was first used in the 2014-2015 season, whereas trivalent split-virion influenza vaccines had been used in previous seasons. We estimate the effectiveness of the subunit vaccine in the current season and split vaccine in the two previous seasons against laboratory-confirmed influenza in the 2014-2015 season.
  
  
  METHODS
  Patients with influenza-like illness hospitalized or attended by sentinel general practitioners were swabbed for influenza testing. The previous and current vaccine status of laboratory-confirmed cases was compared to test-negative controls.
  
  
  RESULTS
  Among 1213 patients tested, 619 (51%) were confirmed for influenza virus: 52% influenza A(H3N2), 46% influenza B, and 2% A(H1N1)pdm09. The overall effectiveness for subunit vaccination in the current season was 19% (95% confidence interval [CI]: -13 to 42), 2% (95%CI: -47 to 35) against influenza A(H3N2) and 32% (95%CI: -4 to 56) against influenza B. The effectiveness against any influenza was 67% (95%CI: 17-87) for 2012-2013 and 2013-2014 vaccination only, 42% (95%CI: -31 to 74) for 2014-2015 vaccination only, and 38% (95%CI: 8-58) for vaccination in the 2012-2013, 2013-2014 and 2014-2015 seasons. The same estimates against influenza A(H3N2) were 47% (95%CI: -60 to 82), -54% (95%CI: -274 to 37) and 28% (95%CI: -17 to 56), and against influenza B were 82% (95%CI: 19-96), 93% (95%CI: 45-99) and 43% (95%CI: 5-66), respectively.
  
  
  CONCLUSIONS
  These results suggest a considerable residual protection of split vaccination in previous seasons, low overall effectiveness of current season subunit vaccination, and possible interference between current subunit and previous split vaccines.
authors: Instituto de Salud Pública de Navarra, IdiSNA-Navarra Institute for Health Research, Pamplona, Spain; CIBER Epidemiología y Salud Pública (CIBERESP), Spain. Electronic address: jcastilc@navarra.es.
authors: Jesús
authors: J
authors: Castilla
authors: Complejo Hospitalario de Navarra, IdiSNA-Navarra Institute for Health Research, Pamplona, Spain.
authors: Ana
authors: A
authors: Navascués
authors: Clínica Universidad de Navarra, IdiSNA-Navarra Institute for Health Research, Pamplona, Spain.
authors: Mirian
authors: M
authors: Fernández-Alonso
authors: Clínica Universidad de Navarra, IdiSNA-Navarra Institute for Health Research, Pamplona, Spain.
authors: Gabriel
authors: G
authors: Reina
authors: Centro Nacional de Microbiología (WHO National Influenza Centre-Madrid), Instituto de Salud Carlos III, Majadahonda, Spain.
authors: Francisco
authors: F
authors: Pozo
authors: Instituto de Salud Pública de Navarra, IdiSNA-Navarra Institute for Health Research, Pamplona, Spain; CIBER Epidemiología y Salud Pública (CIBERESP), Spain.
authors: Itziar
authors: I
authors: Casado
authors: Instituto de Salud Pública de Navarra, IdiSNA-Navarra Institute for Health Research, Pamplona, Spain; CIBER Epidemiología y Salud Pública (CIBERESP), Spain.
authors: Marcela
authors: M
authors: Guevara
authors: Instituto de Salud Pública de Navarra, IdiSNA-Navarra Institute for Health Research, Pamplona, Spain; CIBER Epidemiología y Salud Pública (CIBERESP), Spain.
authors: Iván
authors: I
authors: Martínez-Baz
authors: Instituto de Salud Pública de Navarra, IdiSNA-Navarra Institute for Health Research, Pamplona, Spain; CIBER Epidemiología y Salud Pública (CIBERESP), Spain.
authors: Aurelio
authors: A
authors: Barricarte
authors: Complejo Hospitalario de Navarra, IdiSNA-Navarra Institute for Health Research, Pamplona, Spain.
authors: Carmen
authors: C
authors: Ezpeleta
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype; D053122:Influenza A Virus, H3N2 Subtype; D009981:Influenza B virus; D007252:Influenza Vaccines / Q000627:therapeutic use*; D007251:Influenza, Human / Q000453:epidemiology / Q000517:prevention & control*; D008297:Male; D008875:Middle Aged; D012621:Seasons; D018571:Sentinel Surveillance; D013030:Spain / Q000453:epidemiology; D014611:Vaccination / Q000706:statistics & numerical data*; D022223:Vaccines, Subunit / Q000627:therapeutic use; D055815:Young Adult
chemical_list: D007252:Influenza Vaccines; D022223:Vaccines, Subunit
keywords: Influenza; Influenza vaccine; Split-virion vaccine; Subunit vaccine; Vaccine effectiveness