Analysis Of The Epidemiological Characteristics And Antibody Levels Of Pertussis In Jilin Province,2017–2020

Objective:An analysis of the epidemiological characteristics of pertussis and antibody levels of pertussis in healthy populations in Jilin province from 2017 to 2020 is conducted to understand the three-interval distribution of pertussis,incidence hotspot areas,and the current status of antibody levels of pertussis,and further to estimate the actual level of pertussis infection in the population,so as to provide the optimization of the pertussis surveillance system and the adjustment of immunization strategies in Jilin province scientific basis.Methods:The epidemiological data of pertussis in Jilin province from 2017 to 2020 were obtained from the“Infectious Disease Surveillance Information Reporting Management System”in the“China Disease Control and Prevention Information System”,which included information such as gender,age,occupation,region,and case classification.A total of 103 cases were screened according to the date of onset,and duplicate cases were removed.Excel 2019 and IBM SPSS Statistics 24.0 software were applied to create a database for data processing and analysis to describe the epidemiological characteristics of pertussis in Jilin province.Arc GIS 10.3 software was used to conduct spatial autocorrelation analysis to explore the spatial epidemiological characteristics of pertussis in Jilin province from 2017 to 2020.The healthy population was obtained from the 2017–2020 pertussis surveillance program in Jilin province,and a total of 4168 healthy people without cough,wheezing,and other respiratory symptoms within the last 3 months were selected as study participants,whose venous blood was collected and information related to gender,age and immunization status was collected according to a uniformly designed questionnaire.The enzyme-linked immunosorbent assay was used to detect antibody to PT Ig G.The Geometric Mean Concentration of antibody was compared between groups by the U test or H test.The?² test or Fisher’s exact probability method was applied to analyze whether there were differences in the seropositivity rate and recent infection rate of pertussis in different groups.The differences were regarded as statistically significant at P<0.05.Results:1.Epidemiological distribution characteristics of pertussis in Jilin province from 2017–2020.（1）A total of 103 cases of pertussis were reported in Jilin province in 2017–2020,with 93 cases reported in the province,accounting for 94.90%of the cases.The average yearly number of cases and the average yearly incidence rate were 23 cases and0.09/100,000,respectively,with an overall trend of rising and then declining incidence.Pertussis can develop throughout the year,with the highest incidence months being August-December.The top three areas in terms of incidence rate were 0.18/100,000 in Baicheng City,0.13/100,000 in Jilin City and 0.10/100,000 in Changchun City,while the lowest was in Siping City,with an incidence rate of 0.03/100,000.In terms of gender composition,the female incidence rate was higher than that of male except in 2017.The age of patients was concentrated in 0-6 years old,and children in the diaspora and children in early childhood care were the main incidence groups.（2）The results of global spatial autocorrelation analysis revealed that the spatial distribution of pertussis incidence in Jilin province in 2019 showed high-value clustering,and the incidence of pertussis in 2017,2018 and 2020 showed spatial random distribution.（3）Local spatial autocorrelation analysis showed that there were 11 hot spot regions and 1 cold spot region in Jilin province cumulatively from 2017 to 2020.Among them,the hot spot areas were mainly concentrated in the western and central regions of Jilin province,while the cold spot area was situated in the southwest of Jilin province;8 regions in Jilin province cumulatively had high value aggregation and 4 regions had high value surrounded by low value in 2017–2020,with high value aggregation mainly in the northwest and central regions of Jilin Province and high value surrounded by low value mainly in the southwest of Jilin Province.2.PT Ig G antibody levels in healthy populations in Jilin province,2017–2020.（1）In this study,a total of 3893 qualified blood specimens were collected,and the PT Ig G GMC of pertussis was 7.43 IU/m L,the number of positive antibodies was 399in total,with an antibody positivity rate of 10.25%,and the number of recent infections was 110 in total,with a recent infection rate of 2.83%.（2）The highest PT Ig G GMC,antibody positivity,and recent infection rates between 2017 and 2020 were all in 2017,with results of 8.90 IU/m L,15.74%,and5.03%,respectively,and the lowest were all in 2020,with results of 6.81 IU/m L,8.05%,and 1.54%,respectively.The differences between GMC,seropositivity and recent infection rates between different years were statistically significant（P<0.001）,and the seropositivity and recent infection rates showed a trend of gradual decrease with the increase of years(P _trend<0.001).（3）The PT Ig G GMC,rates of antibody positivity and recent infection between the different sexes were 7.98 IU/m L,12.20%,3.29%for males and 7.12 IU/m L,9.08%,2.55%for females,respectively.By comparison,the differences in GMC and antibody positivity rates between genders were statistically significant（P<0.05）and the differences in recent infection rates were not statistically significant（P>0.05）.（4）The highest PT Ig G antibody GMC,antibody positivity rate and recent infection rate among different regions were all in Tonghua city,with results of 17.07IU/m L,27.50%and 10.83%,respectively,while the lowest regions were all in Baicheng city,with results of 4.10 IU/m L,2.00%and 0.00%,respectively.Upon comparison,the differences in PT Ig G antibody GMC,antibody positivity rate and recent infection rate between regions were statistically significant（P<0.001）.（5）In this survey,the study population was divided into 8 age groups,in which the highest PT Ig G antibody GMC was in the≥50 years group with 9.15 IU/m L and the lowest age group was in the 2-4 years group with 6.10 IU/m L;the highest seropositivity rate and recent infection rate were in the 15-19 years group and the lowest were in the2-4 years and≥50 years groups,respectively.Upon comparison,the differences in PT Ig G GMC and antibody positivity rates between different age groups were statistically significant（P<0.05）,and the differences in recent infection rates were not statistically significant（P>0.05）.The differences in PT Ig G GMC and seropositivity rates between the immunization planning age group（≤14 years old group）and the non-immunization planning group（>14 years old group）were statistically significant（P<0.05）,and the differences in recent infection rates were not statistically significant（P>0.05）.（6）In this investigation,436 individuals aged≤14 years with a history of complete diphtheria vaccination were classified into 5 groups based on the interval between the time of serum sampling and the time of the last dose of pertussis vaccination.the highest PT Ig G antibody GMC and positive rates were in the group with an interval of≥10years,and the lowest were in the group with an interval of 2-3 years and an interval of6-9 years,respectively.Upon comparison,the differences in PT Ig G antibody GMC and serum antibody positivity rates among the populations with different time intervals were statistically significant（P<0.05）,and the serum antibody positivity rates showed a trend of decreasing and then increasing with increasing intervals(P _trend<0.05).（7）To avoid vaccination affecting antibody levels,survey subjects≥14 years old were selected for pertussis infection level assessment in this study.The total number of≥14-year-old survey subjects was 2787,and the recent infection rate was 2.76%（95%CI:2.21%-3.44%）.The estimated infection rate of pertussis in the healthy population aged≥14 years in Jilin province was estimated to be 17.22%（95%CI:13.77%-21.44%）.Conclusion:In this study,by analyzing the epidemiological distribution characteristics of pertussis and the antibody levels of pertussis in healthy populations in Jilin Province from 2017 to 2020,the following conclusions were drawn:（1）The incidence of pertussis in Jilin Province in 2017–2020 exhibited an upward and then downward trend,with incidence throughout the year and the highest incidence in 2019.The areas with higher incidence were Baicheng City,Jilin City and Changchun City.Compared to males,females had higher incidence.The age of incidence was mainly concentrated in 0-6 years old,and the incidence population was mainly diaspora children and children in early childhood care.（2）There was spatial aggregation of pertussis incidence in Jilin province in 2017–2020,with high incidence aggregation areas mainly located in the central and western regions,with more high incidence aggregation areas in parts of Baicheng City,Jilin City and Changchun City,which were the focused areas for prevention and control of pertussis in Jilin province.（3）The antibody levels,seropositivity rates,and recent infection rates in healthy populations of pertussis in Jilin province from 2017 to 2020 demonstrated a decreasing trend.There were differences in antibody levels,seropositivity rates between different genders,regions and age groups.Among them,adolescent and adult groups have higher antibody levels and underestimated infection rates,and have become a priority population for pertussis infection.