Abstract: Objective To analyze the causes of abnormal fluctuations in the incidence of pertussis in Mianyang City,and to explore the immune persistence of pertussis-containing vaccines in the real world. Methods The clinical diagnosis and confirmed cases of pertussis reported from 2005 to 2023 were collected through the information system of China Center for Disease Control and Prevention,and the data were analyzed. Results The average annual reported incidence of pertussis in Mianyang City from 2005 to 2023 was 1.0205/100 000,and the reported incidence was on the rise（ χ²=5 841.464,P<0.01）. The average annual reported incidence of pertussis in the population born from 2000 to 2023 was 99.542 9/100 000,and the reported incidence was on the rise（ χ²=1 113.018,P<0.01）. From 2005 to 2023,the proportion of pertussis cases in the 0-<6 age group in Mianyang City was 63.93%,of which 41.12% were in the 0-<1 year old group. Cases during the diphtheria and tetanus toxoid with acellular pertussis combined vaccine（DTaP） period（born from 2009 to 2023） accounted for 95.37% of all reported cases. The cases without immunization history accounted for 18.51%. Among the cases aged 3-<18 months,71.37% did not complete the corresponding 1-3 doses of immunization program in time. Among the cases aged ≥18 months,93.14% completed the 4 doses of full immunization. The proportion of incidence within 1 month after the completion of 1-3 doses of pertussis-containing vaccine immunization was 61.54%,41.67% and 3.57%,respectively. The proportion of incidence within 5 years after immunization of 4 doses of diphtheria,tetanus and pertussis combined vaccine（DTP）,diphtheria,Tetanus,Acellular Pertussis and Haemophilus Influenzae Type b Combined Vaccine（DTaP -Hib） and diphtheria,tetanus,pertussis（acellular,component）,poliomyelitis（inactivated） vaccine and Haemophilus type b conjugate vaccine,adsorbed,DTaP-IPV-Hib]DTaP-IPV-Hib were 67.19%,97.01% and 84.62%,respectively. Conclusion The abnormal fluctuation of pertussis incidence in Mianyang City from 2005 to 2023 has been affected by many factors,such as the failure of the appropriate age group to complete timely vaccination with pertussis-containing vaccines,the conversion of diphtheria and tetanus toxoid with whole cell pertussis combined vaccine（DTwP） to DTaP,the promotion of polymerase chain reaction detection technology,and the strengthening of doctors' diagnostic awareness. The immune persistence induced by 4 doses of pertussis-containing vaccine was not long. It is recommended to carry out active surveillance of pertussis nationwide,complete the whole course of DTP vaccination for school-age children as soon as possible according to the recommendations of WHO,and optimize the immunization strategy of pertussis vaccine for the whole population.

Key words: Pertussis, Immune characteristics, Retrospective investigation, Immune persistence