title: [Immunity to diphtheria among adults older than 65 years].
abstract: OBJECTIVE
  To know the immune state against diphtheria through a survey, a consultation of the vaccination documents and a seroepidemiologic study of an old population.
  
  
  METHODS
  The immunization status and the prevalence of antidiphtheria antibodies were determined in a representative sample (n = 231) of this population group (> 65 years). Concentrations of toxin antibodies were measured using a commercial ELISA kit. Samples with titres > 0.1 UI/ml were considered protective.
  
  
  RESULTS
  In the vaccination documents we only found 19 old individuals vaccinated against tetanus-diphtheria. 47.1% had no protective titres. Geometric mean titres were 0.12 UI/ml. There was no statistically significant difference between the variables age and sex and the prevalence of antibodies. 84.4% of the 122 seropositives did not report having received diphtheria vaccine and neither had documents about the vaccination.
  
  
  CONCLUSIONS
  There were almost no documents about diphtheria vaccination. Therefore, the serologic study is the only reliable way to know the immunity status against diphtheria in elderly people. Approximately 50% of this population need primary immunization. The rest of this group need to have completed antidiphtheria vaccination or a dose booster within a period of 2 years in order to guarantee protective antibody levels against diphtheria.
authors.affiliation: Centro de Salud Segovia 1, Segovia, Spain. cvelardemayol@yahoo.es
authors.forename: Cristina
authors.initials: C
authors.lastname: Velarde-Mayol
authors.forename: Jose Angel
authors.initials: JA
authors.lastname: Gómez de Caso
authors.forename: Angel
authors.initials: A
authors.lastname: Gil de Miguel
mesh_terms: D000368:Aged; D000907:Antibodies, Bacterial / Q000097:blood; D004165:Diphtheria / Q000276:immunology* / Q000517:prevention & control; D004167:Diphtheria Toxin / Q000276:immunology*; D004168:Diphtheria Toxoid / Q000276:immunology*; D005260:Female; D006801:Humans; D007110:Immunity, Active; D008297:Male; D016036:Seroepidemiologic Studies; D013030:Spain
chemical_list: D000907:Antibodies, Bacterial; D004167:Diphtheria Toxin; D004168:Diphtheria Toxoid