In 1990, the pertussis antibody level was detected in population of 206 persons, who were inoculated with DPT vaccine containing 4?5 billion bacillus pertussis/ml, the protection rate reached 34?47%.

• 1990年使用含百日咳菌45亿/ml百日破混合制剂（DPT），对206人检测抗体水平，保护率为34?47%25；