title: Effectiveness of pneumococcal vaccination for elderly people in Catalonia, Spain: a case-control study.
abstract: BACKGROUND
  Observational studies offer an approach to evaluating the effectiveness of vaccination programs. We evaluated the effectiveness of a 23-valent pneumococcal vaccination program for elderly people in Catalonia, Spain, in a matched-set case-control study.
  
  
  METHODS
  We identified 149 cases of invasive pneumococcal disease among patients aged > or =65 years who were hospitalized in 12 large hospitals in Catalonia during the period of 1 January 2001 through 31 March 2002. We selected 2 hospital control patients and 1 outpatient control subject for each case patient, matching on the basis of age and underlying medical conditions. We obtained their pneumococcal vaccination histories and used conditional logistic regression to determine effectiveness of vaccination.
  
  
  RESULTS
  Among all 149 cases of invasive pneumococcal disease, 131 (87.9%) were caused by vaccine or vaccine-related serotypes. In the adjusted analysis, overall effectiveness of vaccination against infections due to all serotypes was 70% (95% confidence interval [CI], 48%-82%). Among immunocompetent subjects with or without high-risk conditions, effectiveness of vaccination was 76% (95% CI, 51%-88%), but among immunocompromised subjects it was 50% (95% CI, -44% to 82%). Among subjects with infections due to vaccine or vaccine-related serotypes, effectiveness of vaccination was 72% (95% CI, 50%-85%) overall and 78% (95% CI, 50%-90%) in those who were immunocompetent, but it was only 46% (95% CI, -54% to 81%) in those who were immunocompromised. Overall effectiveness of vaccination was 65% (95% CI, 35%-81%) during the noninfluenza period.
  
  
  CONCLUSIONS
  Pneumococcal vaccination was effective in preventing invasive pneumococcal disease among all elderly persons in Catalonia. Effectiveness was greater in immunocompetent persons, most of whom had underlying high-risk conditions. The number of subjects was too small to determine whether vaccination was effective in those who were immunocompromised.
authors.affiliation: Department of Health, Generalitat of Catalonia, Barcelona, Spain. angela.dominguez@gencat.net
authors.forename: Angela
authors.initials: A
authors.lastname: Dominguez
authors.forename: Lluis
authors.initials: L
authors.lastname: Salleras
authors.forename: David S
authors.initials: DS
authors.lastname: Fedson
authors.forename: Conchita
authors.initials: C
authors.lastname: Izquierdo
authors.forename: Laura
authors.initials: L
authors.lastname: Ruiz
authors.forename: Pilar
authors.initials: P
authors.lastname: Ciruela
authors.forename: Asuncion
authors.initials: A
authors.lastname: Fenoll
authors.forename: Julio
authors.initials: J
authors.lastname: Casal
mesh_terms: D000368:Aged; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D016867:Immunocompromised Host; D008297:Male; D016017:Odds Ratio; D011008:Pneumococcal Infections / Q000276:immunology* / Q000517:prevention & control*; D022242:Pneumococcal Vaccines / Q000276:immunology*; D012307:Risk Factors; D013030:Spain
chemical_list: D022242:Pneumococcal Vaccines