Analysis Of The Pertussis Incidence Trends And Influencing Factors In Several Areas Of China From 2004 To 2021

Objective:To analyze pertussis trends in several areas of China from 2004 to 2021;To analyze the effects of different DTa P periods and disease surveillance methods on the incidence of pertussis.Methods:Based on the average annual reported incidence of pertussis in 2017-2019,we selected10 regions in 5 provinces in eastern,central and western China.We obtained pertussis case data and demographic data reported in 10 prefectures during 2004-2021 from the Chinese Disease Control and Prevention Information System and obtained information on diphtheria,tetanus and acellular pertussis combined vaccine(DTa P)immunization and pertussis surveillance strategies with a questionnaire-based survey.We used a Joinpoint regression model to estimate the age-standardized incidence rate(ASIR)of pertussis and its annual percent change(APC)and average annual percent change(AAPC).The incidence rate ratio(RR)was calculated by negative binomial regression model to analyze the effects of different DTa P periods and disease surveillance methods on the incidence of pertussis.Results:1.All study prefectures replaced diphtheria,tetanus and whole-cell pertussis combined vaccine with DTa P from 2007 to 2010.Shandong Province,Guangdong Province,Hunan Province and Shaanxi Province successively conducted intensive pertussis surveillance or pertussis-specific research during 2011-2021.2.Annual average ASIRs ranged from 0.20 to 3.50 per 100 000 population during 2004-202 l,with AAPCs ranging from 4.06% to 44.15% in 6 areas and from-8.77% to-1.11% in4 areas.APCs ranged from 31.20% to 132.70% between the first regression turning point and the second turning point and from-28.77% to-80.70% between the second turning point and 202 l,the end of the study period.3.Multivariate negative binomial regression analysis showed that the risk of pertussis within 5 years after DTa P was completely replaced by DTw P in Yan ’an,Changsha,Zhanjiang and Yueyang was 0.16-0.72 times higher than that before complete replacement.The risk of pertussis within 5 years after DTa P was completely replaced by DTw P in other 6regions was 1.14-12.46 times higher than that before complete replacement.The 5-year risk of pertussis after DTa P completely replacing DTw P in 8 regions except Zhanjiang and Yan’an was 5.08-103.57 times higher than that before complete replacement.The risk of pertussis in the study area with intensive surveillance and pertussis-specific research was1.48-6.49 times and 1.45-3.14 times higher than that without intensive surveillance and pertussis-specific research,respectively.Conclusion:1.The incidence of pertussis initially increased and subsequently decreased during 2004-2021 in all study areas.2.The increasing pertussis incidence have been associated with the improvement of pertussis surveillance capacity by carrying out intensive surveillance and pertussis-specific research、 the substitution of DTa P for DTw P and the waning protection persistence of DTa P.The risk of pertussis increased in 5 years after DTa P completely replaced DTw P.3.The decreasing pertussis incidence may be related to non-drug interventions and the decreasing hospital visits during the epidemic of COVID-19,and the incidence of pertussis may be underestimated.