| BackgroundSince 1980s,many developed countries,such as the United States and Australia,have seen a rise in pertussis while maintaining a high pertussis vaccine coverage rate,which is called"pertussis resurgence".The reasons are still unclear.In recent years,the reported incidence of pertussis in China has been increasing year by year.Since 1956,cases of pertussis have been reported through the statutory infectious disease reporting system in Shandong Province.In 1978,Diphtheria Tetanus and Whole-cell Pertussis Combined Vaccine(DTwP)was included in the planned immunization,and since then,the number of reported cases of pertussis has decreased significantly.From 2008 to 2010,Diphtheria Tetanus and Acellular Pertussis Combined Vaccine(DTaP)replaced DTwP vaccine in the immunization of children of suitable age.Despite the high vaccination rate of more than 95%among children,the number of reported whooping cough cases in the province has been increasing year by year since 2014.ObjectiveTo understand the epidemiological characteristics of pertussis in Shandong Province in the vaccine era;to determine whether the epidemic of pertussis in Shandong Province belongs to"pertussis resugrence ".To analyze the influencing factors of "pertussis resugrence" in Shandong Province.MethodEpidemic data were obtained from the Notifiable Infectious Disease Reporting System and the China Disease Prevention and Control Information System.The case investigation data were mainly obtained from the case investigation of pertussis surveillance cases conducted by the Provincial Center for Disease Control and Prevention(CDC)where the reporting unit was located in 2018.The immunization history and vaccination data of DTaP vaccine are from the immunization planning management system of Shandong Province.The data from the medical institution testing capability survey comes from a questionnaire survey conducted by professionals of the Provincial CDC on 503 secondary and above medical institutions in Shandong Province in 2018.Descriptive epidemiological methods were used to analyze the incidence trend,epidemiological characteristics,clinical characteristics and immunization history of pertussis cases in Shandong Province.ARIMA method was used to construct time series and predict the incidence of pertussis.Spatial autocorrelation analysis was used to describe the spatial distribution of pertussis.Using IBM SPSS 20.0 software,χ2 test was used for the rate or composition ratio test.ArcGIS 10.3 and GeoDa 1.12 were used to draw spatial maps and conduct spatial autocorrelation analysis,and the test level was α=0.05.Results1.Epidemiological characteristics of pertussis in Shandong Province:(1)Incidence trend:In 2014,the reported incidence rate of the whole province was 1.08/100,000,which began to rise.The prediction results of the ARIMA model showed that the actual number of cases from 2014 to 2018 was much higher than the predicted number.(2)Disease characteris:①Epidemiological characteristics:distribution characteristics:age distribution:from 2005 to 2018,the highest proportion of cases less than 1 year old was 51.43%.There was significant difference in the age distribution of reported cases between 2005～2013 and 2014～2018(χ2=55.886,P<0.001).From 2014 to 2018,the age distribution difference of reported cases was statistically significant(χ2=291.197,P<0.001),the age group of 15 or above increased from 0 in 2005～2013 to 2014～2018 0.07/10 in the annual incidence rate of 0.07/10 million.The male to female ratio of reported cases from 2005 to 2018 was 1.13:1.The occupational distribution is that scattered children account for 79.80%,nursery children account for 11.87%,students account for 6.55%and others account for 1.77%.The high incidence month of pertussis is from June to August.②Spatiotemporal aggregation and its hot spot distribution:From 2014 to 2018,the global Moran’s I index of pertussis incidence in Shandong Province in each year was all>0,and there was a positive spatial autocorrelation in the incidence of pertussis in each year in Shandong Province,showing obvious spatial aggregation.Pertussis "high-high" agglomeration areas are mainly distributed in the central and western regions.③Case classification:The proportion of laboratory-confirmed cases increased from 11.70%in 2005 to 2013 to 50.63%in 2014 to 2018;there was a statistically significant difference in the composition ratio of reported cases in 2005 to 2013 and 2014 to 2018(χ2=895.399,P<0.001).④Clinical manifestations:The most common is paroxysmal cough,with an incidence of 85.87%.The incidence of crowing-like echo,vomiting,and bruising of the lips was low,all<40%.Complications occurred in 29.50%of cases,the most common being pneumonia.2.Analysis of Influencing Factors of Pertussis Incidence in Shandong Province:(1)DTaP vaccination:Among children less than 1 year old and≥3 months old at the time of onset,71.48%of the pertussis surveillance cases had a history of Diphtheria,Tetanus and Pertussis Combined Vaccine(DTP)vaccination before onset.According to 2 defining criteria for timely vaccination(infants who complete the 1st,2nd,and 3rd doses of DTPa vaccine at the age of 4,5,and 6 months after birth,or before the age of 5,6,and 7 months,are considered to be vaccinated in time).The timely vaccination rates of DTP vaccine were 34.61%and 43.41%,respectively.The timely vaccination rate of the first,second and third doses of DTP vaccine in the cases was lower than the reported timely vaccination rate of DTP vaccine in the whole province.(2)Pertussis etiological and serological detection capabilities of medical institutions:Among the 543 medical institutions in the province,10 medical institutions carry out pertussis IgM,IgG and nucleic acid testing,accounting for 1.84%respectively;2 medical institutions carry out bacterial culture,accounting for 0.37%.20 carry out at least one of the above tests.home,accounting for 3.68%.The proportion of tertiary medical institutions with pertussis IgM,IgG and nucleic acid detection capabilities(6.42%)was significantly higher than that of secondary medical institutions 2.25%(χ2=6.009,P=0.014).From 2010 to 2018,the number of reported cases of pertussis in Shandong Province developed at a rate of 2471.79%on a fixed basis,and the number of medical institutions with detection capabilities was as high as 4533.33%.After 15 medical institutions conducted pertussis etiological and serological testing,the annual average number of reported cases was higher than that before the testing.Conclusions1.For many years,the vaccination rate of DTP vaccine in Shandong Province has been maintained at a high level,but the incidence of pertussis has shown an upward trend since 2014,which has met the definition of recurrence of pertussis.2.The recurring epidemiological characteristics of pertussis in Shandong Province,the reported incidence of pertussis is still mainly in young infants,but the proportion of children and even adults in the older age group has increased compared with before;the reported incidence is clustered in time and space;in terms of clinical manifestations,the current pertussis Symptoms are not typical.3.The lack of timely vaccination with DTP vaccine and the improvement of pertussis etiological and serological detection capabilities of medical institutions may be important factors for the recurrence of pertussis in Shandong Province.Advice1.The etiological and serological diagnostic capabilities of pertussis in secondary and above medical institutions in Shandong Province need to be improved.2.Adjust and improve the immunization strategy of DTP vaccine in a timely manner,and further increase and maintain a high level of DTP timely vaccination rate for school-age children.3.Strengthen the monitoring of pertussis epidemics and the construction of pertussis detection capacity in medical institutions. |
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