[Immunity to diphtheria among adults older than 65 years].
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.
Velarde-Mayol
Cristina
C
Centro de Salud Segovia 1, Segovia, Spain. cvelardemayol@yahoo.es
Gómez de Caso
Jose Angel
JA
Gil de Miguel
Angel
A
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
D000907:Antibodies, Bacterial; D004167:Diphtheria Toxin; D004168:Diphtheria Toxoid