| ObjectiveTo analyze the epidemic characteristics of pertussis in Shenzhen;To evaluate the Vaccine effectiveness(VE)of pertussis vaccine in preschool children and its change trend over time;To explore the correlation between pertussis vaccination and serum pertussis Ig G antibody level.From the two dimensions of macro population research and micro serological investigation,case-control research and cross-sectional research,this paper comprehensively evaluates the protective effect of pertussis vaccine for preschool children in Shenzhen,in order to provide reference basis for improving the immunization strategy of pertussis.MethodsPart Ⅰ.Epidemiological characteristics of pertussis in Shenzhen from 2016 to 2020The data of pertussis cases reported in Shenzhen,Guangdong Province from 2016 to2020 were derived from the infectious disease monitoring module of China disease prevention and control information system to describe the epidemiological characteristics of pertussis in Shenzhen.Part Ⅱ.Case-control study on the protective effect of pertussis vaccine in preschool childrenA 1:1 matched case-control study was conducted.The case group was selected from the clinically diagnosed and confirmed cases of pertussis whose current address was Shenzhen,the reporting date was 2019,and the age at the time of onset was≤6 years old.The control group was matched according to the matching principles of the same living community,birth date and gender as the case group,Children without pertussis report records were selected from Shenzhen immunization planning information management system by random number method.Using the binary conditional logistic regression model,the odds ratio(OR)and its confidence interval(CI)were calculated to explore the Vaccine effectiveness(VE)of pertussis vaccine containing anti pertussis component in preschool children in Shenzhen and its change trend over time from four aspects:overall Vaccine effectiveness,vaccine type,immune status and whole course immunization interval.PartⅢ.Serological investigation of pertussis antibody level in preschool childrenUsing Multistage sampling method,296 preschool children aged 4-6 years old who had been vaccinated with anti pertussis component vaccine and had no symptoms such as paroxysmal or spastic cough were selected as the research objects in the maternal and child health centers of Luohu District,Nanshan District and Bao’an District of Shenzhen.Carry out face-to-face field epidemiological questionnaire survey,and collect the basic demographic information,past medical history and immunization planning and vaccination information of the subjects in combination with Shenzhen immunization planning information management system;The geometric mean concentration(GMC)of pertussis Ig G antibody was measured quantitatively by enzyme-linked immunosorbent assay(ELISA),and the positive conversion rate of pertussis Ig G antibody was calculated.Using non conditional multivariate logistic regression model,taking whether the antibody is positive or not as the dependent variable,demographic information such as age,gender and region were analyzed to evaluate the correlation between vaccination time,dose,vaccine type and serum pertussis Ig G antibody level,and the odds ratio(OR)was calculated.ResultsEpidemiological characteristics of pertussis in Shenzhen from 2016 to 2020In the 2016-2020 year,4883 cases of pertussis were reported in Shenzhen city of Guangdong Province,with an average annual incidence of 977 cases,with an average annual incidence rate of 7.48/10 million.The number of reported cases of pertussis increased from 456 cases to 1879 cases in 2016-2019 years,and the incidence rate increased from 3.83/10 to 13.98/10 million.Scattered children and nursery children are the main population,and the majority of preschool children younger than 7 years old account for 93.79%;It is the highest in the third quarter of each year(i.e.July September);Longgang District,Bao’an District and Guangming district are the top three districts in the cumulative number of reported cases;The top three hospitals reported cases were Shenzhen Children’s Hospital,Shenzhen Bao’an maternal and child health hospital and Shenzhen Hospital of Beijing University of traditional Chinese medicine.Case-control study on the protective effect of pertussis vaccine in preschool children1038 cases and 1038 controls were finally included in this study.The gender ratio of men and women was 1.13:1.The total Vaccine effectiveness(VE)of the vaccine was90.75%(95%CI:86.78%-95.52%),and the protective effect of partial immunization was 84.56%(95%CI:76.99%-89.64%);The protective effect of whole course immunization was 91.45%(95%CI:85.80%-94.86%),and the protective effects of triple(DTa P),quadruple(DTa P-Hib)and quintuple(DTa P-IPV/Hib)vaccines were86.10%(95%CI:80.26%-90.21%),92.59%(95%CI:77.77%-97.53%)and 91.89%(95%CI:79.74%-96.76%)respectively.From January to November,December to 23,24-35 The protective effects from 36 to 60 months were 92.68%(95%CI:86.23%-96.11%),88.64%(95%CI:80.48%-93.38%),84.91%(95%CI:71.28%-92.07%)and79.41%(95%CI:57.08%-90.12%)respectively.Serological investigation of pertussis antibody level in preschool childrenA total of 296 preschool children in Shenzhen were included in this study,including153 boys and 143 girls;There are 115,114 and 67 children aged 4,5 and 6 respectively,and 100,96 and 100 children in Nanshan District,Luohu District and Bao’an District respectively.The total positive rate of pertussis Ig G antibody in preschool children in Shenzhen was 20.27%,and the positive rates of children aged 4,5 and 6 were 20.00%,17.54%and 25.37%respectively(χ~2=1.61,P=0.447);The whole course immunization group and partial immunization group were 21.35%and 0.00%respectively(Fisher exact probability method,P=0.047);The timely and extended vaccination groups were 21.46%and 20.97%respectively(χ~2=0.01,P=0.990);The rates of<24 months,24-35 months,36-47 months and≥48 months were 30.77%,23.17%,20.49%and 18.75%respectively(trendχ~2=-0.79,P=0.429).The GMC of total pertussis Ig G antibody was 9.04U/ml,that of whole course immunization group was 9.31U/ml,and that of partial immunization group was 5.18U/ml(t=-5.17,P=0.001);12.48U/ml in timely vaccination group and8.74U/ml in overdue vaccination group(t=2.01,P=0.048);The triple group,quadruple group and quintuple group were 8.40U/ml,13.16U/ml and 26.65U/ml respectively(F=5.60,P=0.019).The two classification multivariate logistic regression model finally included four variables:vaccine completion(OR=46.15,95%CI:6.850～484.9),vaccine type of pentavalent vaccine(OR=25.87,95%CI:7.740～119.7),age(OR=2.315,95%CI:1.587～3.442)and timely vaccination of the first injection(OR=2.101,95%CI:0.413～8.598).ConclusionThe incidence risk of pertussis in Shenzhen is increasing rapidly.The population of pertussis is mainly concentrated in preschool children.The risk of pertussis may be increased when kindergartens start school in spring and summer.Pertussis monitoring should be done well before school starts.The overall protective effect of pertussis vaccine for preschool children in Shenzhen was good,but it showed a decreasing trend with the passage of time;The geometric mean concentration and positive conversion rate of pertussis Ig G antibody were low.The geometric mean concentration and positive conversion rate of pertussis Ig G antibody could be improved by whole course and timely vaccination of pertussis vaccine.Shenzhen social health doctors should urge parents to complete the vaccination in time and in the whole process;The strategy of strengthening the needle of pertussis vaccination for preschool children and the strategy of"cocoon"vaccination for people around newborns should be accelerated. |
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