Seroprevalence of pertussis among adults in China where whole cell vaccines have been used for 50 years

Objective: To estimate the true incidence of pertussis in Chinese adults who are at a childbearing age. Methods: A total of 897 serum samples from healthy individuals aged 20-39 years were selected randomly from a large number of serum samples collected in 2010 in Beijing, China. Anti-pertussis toxin (Ptx) IgG antibodies were determined with the Virion/Serion ELISA kits using purified Ptx as a coating antigen. Results: Only 124 (13.8%) were found to have undetectable anti-Ptx IgG antibodies. The mean concentration was 13.76 IU/ml (95% CI, 12.37-15.15). Forty-six (5.1%) subjects had anti-Ptx IgG levels greater than or equal to 40 IU/ml, indicative of a pertussis infection, and nine (1%) had IgG antibodies greater than or equal to 100 IU/ml, indicative of a recent infection within a year. No significant differences were observed between age groups of 20-29 and 30-39 years, or between genders. Conclusions: Our study showed that about 5% of adults aged 20-39 years had positive anti-Ptx IgG antibodies, suggesting that adult pertussis is common in China. Giving a booster vaccination to pregnant women should possibly be considered in order to protect young infants who are too young to be vaccinated in this country. (C) 2016 The British Infection Association. Published by Elsevier Ltd. All rights reserved.