title: Interim influenza vaccine effectiveness: A good proxy for final estimates in Spain in the seasons 2010-2014.
abstract: BACKGROUND
  The agreement between interim and final influenza vaccine effectiveness (VE) estimates would support the use of interim assessments as a proxy for final VE results to guide health authorities in influenza prevention. We aimed to compare interim/final VE estimates in Spain.
  
  
  METHODS
  We used a test-negative case-control study (cycEVA) for 2010/11-2013/14 seasons. Sensitivity analyses were carried out by type/subtype of influenza virus and by target groups for vaccination.
  
  
  RESULTS
  In general, interim estimates were higher compared to end-season estimates. Interim and final VE differences were higher for the target groups compared to all population. Subtype-specific interim/final VE estimates showed greater concordance (3-13%) than for any virus (7-24%).
  
  
  CONCLUSIONS
  In Spain, interim influenza VE estimates over 2010-2014 were a good proxy of the final protection of the vaccine. Interim and final estimates showed greater concordance for all population and if performed subtype-specific.
authors: National Centre of Epidemiology, Institute of Health Carlos III, c/Monforte de Lemos no.5, 28029 Madrid, Spain; CIBER Epidemiología y Salud Pública (CIBERESP), Institute of Health Carlos III, Madrid, Spain. Electronic address: silviajimenezjorge@gmail.com.
authors: Silvia
authors: S
authors: Jiménez-Jorge
authors: Institute of Health Carlos III, National Centre for Microbiology, National Influenza Centre, 28220 Majadahonda, Madrid, Spain. Electronic address: pacopozo@isciii.es.
authors: Francisco
authors: F
authors: Pozo
authors: National Centre of Epidemiology, Institute of Health Carlos III, c/Monforte de Lemos no.5, 28029 Madrid, Spain; CIBER Epidemiología y Salud Pública (CIBERESP), Institute of Health Carlos III, Madrid, Spain. Electronic address: alarrauri@isciii.es.
authors: Amparo
authors: A
authors: Larrauri
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; D007223:Infant; D007231:Infant, Newborn; D007252:Influenza Vaccines / Q000008:administration & dosage / Q000276:immunology*; D007251:Influenza, Human / Q000453:epidemiology* / Q000517:prevention & control*; D008297:Male; D008875:Middle Aged; D018571:Sentinel Surveillance; D013030:Spain / Q000453:epidemiology; D016896:Treatment Outcome; D014611:Vaccination / Q000379:methods*; D055815:Young Adult
chemical_list: D007252:Influenza Vaccines
keywords: Case-control studies; Influenza; Interim analysis; Sentinel networks; Vaccine effectiveness