Seroprevalence of antibodies for pertussis and diphtheria among people leaving or entering China: a cross-sectional study

Abstract

Introduction: Despite high population immunity, pertussis remains one of the leading causes of vaccine-preventable deaths worldwide. The aim of this study was to determine the seroprevalence of IgG antibodies to pertussis toxin (PT) and diphtheria among the adult male population leaving or entering China. Methodology: Blood samples were obtained from 240 Chinese and 207 African healthy adults that were leaving and entering China, respectively. Serum IgG antibodies against PT (anti-PT IgG) and diphtheria were determined. Results: The mean concentration of anti-PT IgG antibodies was 13.82 IU/mL and 18.11 IU/mL for the leaving and entering populations, respectively. None of the studied Chinese leaving China were seropositive for pertussis. Of the 240 subjects leaving China, 209 (87.1%) had anti-diphtheria antibody concentrations of ≥ 0.1 IU/mL and 31 (12.9%) had antibody concentrations between 0.01 and 0.099 IU/mL. Eleven (5.31%) of the studied Africans entering China had anti-PT IgG antibodies higher than 30 IU/mL and thus were considered seropositive for pertussis. Of the 207 Africans entering China, antibody concentrations of ≥ 0.1 IU/mL were found in 164 subjects (79.2%) while 43 (20.8%) had antibody concentrations between 0.01 and 0.099 IU/mL. Conclusions: Almost all Chinese adult men leaving China and most African men entering China have very low serum antibody levels of pertussis. Furthermore, the antibody level of diphtheria among these two populations was low among adults. A larger population study is needed to determine whether booster vaccinations against pertussis and diphtheria should be considered for adults in China and also for Africans entering China.