title: Effectiveness of monovalent 2009 pandemic influenza A virus subtype H1N1 and 2010-2011 trivalent inactivated influenza vaccines in Wisconsin during the 2010-2011 influenza season.
abstract: BACKGROUND
  The 2009 influenza A virus subtype H1N1 (A[H1N1]pdm09) did not exhibit antigenic drift during the 2010-2011 influenza season, providing an opportunity to investigate the duration of protection after vaccination. We estimated the independent effects of 2010-2011 seasonal trivalent inactivated influenza vaccine (TIV) and A(H1N1)pdm09 vaccine for preventing medically attended influenza A virus infection during the 2010-2011 season.
  
  
  METHODS
  Individuals were tested for influenza A virus by real-time reverse transcription polymerase chain reaction (rRT-PCR) after a clinical encounter for acute respiratory illness. Case-control analyses compared participants with rRT-PCR-confirmed influenza A virus infection and test-negative controls. Vaccine effectiveness was estimated separately for monovalent pandemic vaccine and TIV and was calculated as 100 × [1 - adjusted odds ratio], where the odds ratio was adjusted for potential confounders.
  
  
  RESULTS
  The effectiveness of TIV against influenza A virus infection was 63% (95% confidence interval [CI], 37%-78%). The effectiveness of TIV against A(H1N1)pdm09 infection was 77% (95% CI, 44%-90%). Monovalent vaccine administered between October 2009 and April 2010 was not protective during the 2010-2011 season, with an effectiveness of -1% (95% CI, -146% to 59%) against A(H1N1)pdm09 infection.
  
  
  CONCLUSIONS
  Monovalent vaccine provided no sustained protection against A(H1N1)pdm09 infection during the 2010-2011 season. This waning effectiveness supports the need for annual revaccination, even in the absence of antigenic drift in A(H1N1)pdm09.
authors: Epidemiology Research Center(ML2), Marshfield Clinic Research Foundation, 1000 N Oak Ave, Marshfield, WI 54449, USA.
authors: Allen C
authors: AC
authors: Bateman
authors: Burney A
authors: BA
authors: Kieke
authors: Stephanie A
authors: SA
authors: Irving
authors: Jennifer K
authors: JK
authors: Meece
authors: David K
authors: DK
authors: Shay
authors: Edward A
authors: EA
authors: Belongia
mesh_terms: D000293:Adolescent; D000328:Adult; D016022:Case-Control Studies; D002648:Child; D005260:Female; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000276:immunology / Q000472:pathogenicity*; D007252:Influenza Vaccines / Q000276:immunology / Q000627:therapeutic use*; D007251:Influenza, Human / Q000453:epidemiology / Q000276:immunology / Q000517:prevention & control* / Q000821:virology; D008297:Male; D008875:Middle Aged; D058873:Pandemics / Q000517:prevention & control*; D012621:Seasons; D014922:Wisconsin / Q000453:epidemiology; D055815:Young Adult
chemical_list: D007252:Influenza Vaccines