Blood samples were obtained from 210 healthy adults aged 18?0 years in Weifang city, China during the period of May and June 2010. Serum IgG antibodies against PT (anti-PT IgG) and diphtheria were determined by the commercial ELISA kits, respectively. According to the kit, concentration of anti-PT IgG higher than 30?IU/mL was considered positive. An antibody concentration of ?.1?IU/mL was defined as evidence of seroprotection against diphtheria.
The mean concentration of anti-PT IgG antibodies was 9.95?IU/mL (95 % confidence interval (CI) 8.45?1.44). Eleven (5.24 % ) of the studied subjects were proved to be seropositive to pertussis. Of the 210 subjects, 161 (76.6 % ) had anti-diphtheria antibody concentration ?.1?IU/mL and 49 (23.3 % ) had the antibody concentration between 0.01 and 0.099?IU/mL.
Our study indicated that about 5 % of adults aged 18?0 years had positive anti-PT IgG antibodies, suggesting that adult pertussis is not uncommon in China. Although a high proportion of studied subjects had a protective level of immunity against diphtheria, the antibody level decreased with the increasing age of adults. Booster vaccinations against pertussis should be considered in adults in China.