To estimate the true incidence of pertussis in Chinese adults who are at a childbearing age.

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.

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.

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.