[Low level of immune protection against diphtheria in adult population of Catalonia].

BACKGROUND

Seroepidemiologic studies carried out in different European countries have shown the existence of low levels of protection against diphtheria. In this study the prevalence of antidiphtheria antibodies in the adult population of Catalonia, Spain, during 1995 has been studied.

PATIENTS AND METHODS

The prevalence of the seroprotection against diphtheria was investigated in a representative sample (n = 1,248) of the adult population 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 > or = 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%: 23.6-28.4%). 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 regression analysis were 1.43 (1.11-1.85) and 1.56 (1.05-2.29), respectively.

CONCLUSION

The prevalence of antidiphtheria antibodies in the adult population of Catalonia, Spain, is low. The results suggest the need to develop antidiphtheria vaccination programmes in the adult population.