title: Seroprevalence of antibodies to pertussis and diphtheria among healthy adults in China.
abstract: OBJECTIVE
  Despite extensive childhood immunization, pertussis remains one of the world's leading causes of vaccine-preventable deaths. Incidence of pertussis in adolescents and adults has increased in many countries despite high vaccination coverage. In China, booster vaccinations against diphtheria, tetanus and pertussis are not used in adults, and little is known about pertussis incidence in the age group. The aim of this study was to determine seroprevalence of IgG antibodies to pertussis toxin (PT) and diphtheria among adults in China.
  
  
  METHODS
  Blood samples were obtained from 210 healthy adults aged 18-50 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 ≥ 0.1 IU/mL was defined as evidence of seroprotection against diphtheria.
  
  
  RESULTS
  The mean concentration of anti-PT IgG antibodies was 9.95 IU/mL (95% confidence interval (CI) 8.45-11.44). 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 ≥ 0.1 IU/mL and 49 (23.3%) had the antibody concentration between 0.01 and 0.099 IU/mL.
  
  
  CONCLUSIONS
  Our study indicated that about 5% of adults aged 18-50 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.
authors.affiliation: Institute for Communicable Disease Control and Prevention, State Key Laboratory of Infectious Diseases, Chinese Center for Disease Control and Prevention, PO Box 5, Changping, Beijing 102206, PR China. zhangqi@chinacdc.cn
authors.forename: Qi
authors.initials: Q
authors.lastname: Zhang
authors.forename: Fulian
authors.initials: F
authors.lastname: Han
authors.forename: Qing
authors.initials: Q
authors.lastname: Nie
authors.forename: Hongyu
authors.initials: H
authors.lastname: Ren
authors.forename: Baoqiang
authors.initials: B
authors.lastname: Zhang
authors.forename: Qiyong
authors.initials: Q
authors.lastname: Liu
authors.forename: Qiushui
authors.initials: Q
authors.lastname: He
authors.forename: Zhujun
authors.initials: Z
authors.lastname: Shao
mesh_terms: D000293:Adolescent; D000328:Adult; D000907:Antibodies, Bacterial / Q000097:blood*; D000992:Antitoxins / Q000097:blood; D002681:China / Q000453:epidemiology; D003430:Cross-Sectional Studies; D004165:Diphtheria / Q000453:epidemiology*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood; D008297:Male; D008875:Middle Aged; D016036:Seroepidemiologic Studies; D014917:Whooping Cough / Q000453:epidemiology*; D055815:Young Adult
chemical_list: D000907:Antibodies, Bacterial; D000992:Antitoxins; D007074:Immunoglobulin G