Low level of protection against diphtheria in adult population of Catalonia Spain

BACKGROUND: Seroepidemiologic studies carried out in different European cou ntries have shown the existence of low levels of protection against diphthe ria. In this study the prevalence of antidiphtheric antibodies in the adult population of Catalonia, Spain, during 1995 has been studied. PATIENTS AND METHODS: The prevalence of the seroprotection against diphther ia was investigated in a representative sample (n = 1,248) of the adult pop ulation of Catalonia aged 15 or older. The antibody levels were determined by means of the in vitro Vero-cell neutralization technique. Two protection levels were considered: 0.01-0.09 U/ml (partial immunity) and greater than or equal to 0.1 U/ml (total immunity). RESULTS: The prevalence of absolute seroprotection was 12.4% (CI 95%: 10.5- 14.3%) and that of partial and absolute seroprotection was 26.0% (CI 95%: 2 3.6-28.4%). The prevalence of antibodies is higher in men than in women (29 .2% versus 23.1%; p < 0.05), and in urban than in rural environments (27.2% versus 19.9%; p < 0.05), The odds ratios adjusted by multiple logistic reg ression analysis were 1.43 (1.11-1.85) and 1.56 (1.05-2.29), respectively, CONCLUSION: The prevalence of antidiphtheric antibodies in the adult popula tion of Catalonia, Spain, is low, The results suggest the need to develop a ntidiphtheric vaccination programmes in the adult population.