The prevalence of diphtheria immunity in healthy population in Poland

The degree of seroprotection against diphtheria in Poland was evaluated by determination of IgG antibodies to Corynebacterium diphtheriae toxin (IgG-D TAb). The study population consisted of 4829 healthy subjects aged from 1 d ay to 85 years from 7 regions of Poland. Serum samples collected between 19 96 and 1998 were assayed for IgG-DTAb antibodies using a toroid enzyme immu noassay. Neutralization of toxin in Vero cells was performed as a reference method with the WHO standard for human diphtheria antitoxin. The study rev ealed a lack of seroprotection (IgG-DTAb < 0.1 IU/mI) in 23 % of individual s, basic seroprotection (0.1-1.0 IU/ml) in 64 %, and effective seroprotecti on (> 1.0 IU/ml) in 13 %. The non-protected group consisted of non-vaccinat ed children below 2 months of age (10%), individuals between 2 months and 1 8 years old (20 %) and greater than 19 years old (70 %). Of the adults, 32 % were seronegative, 63 % had basic seroprotection and only 5 % were fully protected: 43 % of adults between 30 and 64 years, who had not been vaccina ted at least during the previous 10 years were not protected against diphth eria. The geometric mean titre (GMT) of IgG-DTAb was 0.25 IU/ml in the tota l population. Age-related GMTs differed significantly from each other and w ere higher (0.44 IU/ml) in individuals from 2 months to 18 years old, compa red with 0.14 IU/ml and 0.17 IU/ml in children under 2 months and adults, r espectively. No significant difference was found in the GMTs of men and wom en in all age groups. We conclude that the currently used vaccination progr amme in Poland is highly effective and assures protection against diphtheri a in the majority of the population in the 10-year period following the las t booster. However, a significant proportion of adults between 30 and 64 ye ars lack protection and this indicates a need for booster immunization for this group.