title: Decline in influenza vaccine effectiveness with time after vaccination, Navarre, Spain, season 2011/12.
abstract: This study evaluates the influenza vaccine effectiveness (VE) in preventing laboratory-confirmed cases in Navarre, Spain, in the 2011/12 season in which the peak was delayed until week 7 of 2012. We conducted a test-negative case–control study. Patients with influenza-like illness in hospitals and primary healthcare were swabbed for testing by reverse transcription-polymerase chain reaction. Influenza vaccination status and other covariates were obtained from healthcare databases. The vaccination status of confirmed cases and negative controls was compared after adjusting for potential confounders. VE was calculated as (1-odds ratio)x100. The 411 confirmed cases (93% influenza A(H3)) were compared with 346 controls. Most characterised viruses did not match the vaccine strains. The adjusted estimate of VE was 31% (95% confidence interval (CI): -21 to 60) for all patients, 44% (95% CI: -11 to 72) for those younger than 65 years and 19% (95% CI: -146 to 73) for those 65 or older. The VE was 61% (95% CI: 5 to 84) in the first 100 days after vaccination, 42% (95% CI: -39 to 75) between 100 and 119 days, and zero thereafter. This decline mainly affected people aged 65 or over. These results suggest a low preventive effect of the 2011/12 seasonal influenza vaccine, and a decline in VE with time since vaccination.
authors: Instituto de Salud Publica de Navarra (Public Health Institute of Navarre), Pamplona, Spain. jcastilc@navarra.es
authors: J
authors: J
authors: Castilla
authors: I
authors: I
authors: Martínez-Baz
authors: V
authors: V
authors: Martínez-Artola
authors: G
authors: G
authors: Reina
authors: F
authors: F
authors: Pozo
authors: M
authors: M
authors: García Cenoz
authors: M
authors: M
authors: Guevara
authors: J
authors: J
authors: Morán
authors: F
authors: F
authors: Irisarri
authors: M
authors: M
authors: Arriazu
authors: E
authors: E
authors: Albéniz
authors: C
authors: C
authors: Ezpeleta
authors: A
authors: A
authors: Barricarte
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D016001:Confidence Intervals; D005260:Female; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D009980:Influenza A virus / Q000235:genetics* / Q000276:immunology / Q000302:isolation & purification; D007252:Influenza Vaccines / Q000008:administration & dosage / Q000276:immunology*; D007251:Influenza, Human / Q000175:diagnosis / Q000453:epidemiology* / Q000517:prevention & control* / Q000821:virology; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D011320:Primary Health Care; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012621:Seasons; D018571:Sentinel Surveillance; D013030:Spain / Q000453:epidemiology; D013997:Time Factors; D016896:Treatment Outcome; D014611:Vaccination / Q000706:statistics & numerical data; D055815:Young Adult
chemical_list: D007252:Influenza Vaccines