The Epidemiology Of Antibody Against Pertussis,Diphtheriea And Tetanus In Gaobeidian City, Hebei Province

Backgrounds Whooping cough (pertussis) is an acute respiratory infectious disease, which is vaccine preventable and is reportable in China. Paroxymal cough is the typical clinical symptom, and it has a long course with heavy burden of disease. The Pan American Health Organization/World Health Organization (PAHO/WHO)has estimated that50million cases and300000deaths have occurred because of pertussis worldwide in2012. Despite high vaccine coverage, there remains endemic worldwide. In America, the vaccination coverage was high (93%), the reported incidence of pertussis has reached18716per100000in2011. In China, after the introduction of DTP, the incidence of pertussis decreased sharply from prevaccination era, from100-200infections/100OOOpeople to<1infection/100000people during the1990s. The incidence of pertussis was0.2per100000in2012China. The surveillance of pertussis in China is clinical symptom based, and it is lack of sensitive laboratory testing skills. That might be one of reasons causing the underestimation of pertussis in China. Because the symptom of pertussis becomes atypical with the use of DTP. It is also reported that the incidence of adolescents becomes higher and higher, and has become the main source of infection of susceptible infants. The real epidemiology against pertussis in population, especially in the adolescents was unknown in China.The results of prior studies in our laboratory shows that the method of culture and PCR is not quit fit the surveillance of health population. Thus, we use the method of ELISA to test the antibody of PT (pertussis toxin, PT)in serum. PT is the most specific antigen for pertussis, which is also the main antigen of pertussis vaccine. However, nomatter the rising of PT is caused by vaccination or natural infection, it declines quickly. Thus the method of ELISA to test the antibody of PT is widely used to monitor population。However there are no recommended ELISA kits in regular surveillance on pertussis in China.A combined diphtheriatetanus-acellular pertussis vaccine (DTaP) was introduced because of the severe side-effects of wholecell vaccines (DTwP) in2007in China (including Gaobeidian city). After the change of DTP vaccine, the long term effect against diphtheria and tetanus has not been evaluated. Objectives This is a cross sectional study based on schools (including kindergartens, primary schools and secondary schools) and communities in Gaobeidian city, China. We recorded DTP related immune history, tested the antibody level against PT. The aim was to know the epidemiology of pertussis in adolescents and the whole population; to have a knowledge of the changing of PT antibody in population; to compare the long term effect on diphtheria and tetanus between DTwP and DTaP; to provide fundamental data to the establishment of vaccine schedule on DTP in China. Method Firstly, Comprehensively evaluate the stability of in-house commercialBordetellaenzyme-linked immunosorbent assays kits for detection of immunoglobulin G to pertussis toxin (Anti-PT IgG ELISA kit) and imported commercial Bordetella Anti-PT IgG ELISA kit, to provide proof for the chosen of Bordetella Anti-PT IgG ELISA kits to be used in present study. Serum samples are collected between October2012and June2013. Samples are residual specimens collected during regular physical examinations in Gaobeidian city, China, which would otherwise have been discarded.1463serum samples are collected in the whole population.587are sampled from children and adolescents aged2-17years to test the antibodies against diphtheria and tetanus. Interrupted time series method was used to analyze the change of antibodies against diphtheria and tetanus after the replacement of DTP vaccine. Results Firstly, we choose the Anti-PT IgG ELISA kit made by verion (ELISA; Serion ELISA classic, Institut Virion/Serion GmbH, Germany) as the testing tool in our present study. Secondary, the geometric mean of the1463samples was7.59IU/ml (95%CI,7.14-8.07). The positive rate on pertussis (Anti-PT IgG level>40IU/ml) was9.13%; while the recent infection rate (Anti-PT IgG level>100IU/ml) was2.73%. The peak on antibody against PT appeared in adolescents (12-13years old), which declined in subjects at19years old and remained stable after20years old. Thirdly,1032samples were collected from2kindergartens,4primary schools and7secondary schools. The geometric mean of these samples was6.93IU/ml (95%CI,6.42-7.48), The positive rate on pertussis (Anti-PT IgG level>40IU/ml) was9.79%while the recent infection rate (Anti-PT IgG level>100IU/ml) was3.39%. Clustered cases were found in3secondary schools. Forth, the geometric mean of antibody against diphtheria in587samples was0.074IU/ml (95%CI,0.065-0.084), the positive rate on diphtheria (antibody level>0.01IU/ml) was88.25%; the geometric mean of antibody against tetanus in587samples was0.063IU/ml (95%CI,0.053-0.076), the positive rate on tetanus (antibody level>0.01IU/ml) was82.11%. Antibodies on diphtheria and tetanus declined with the time gone by, however, the antibodies on diphtheria and tetanus declined slower in DTwP than DTaP. Conclusions Pertussis was still circulating in Gaobeidian city, China, especially in adolescents. Clustered cases were found in adolescents. The protection rate against diphtheria on children and adolescents was sufficient to prevent diphtheria outbreak at present. Antibodies against diphtheria and tetanus declined with the time gone by, and the antibodies on diphtheria and tetanus declined slower in DTwP than in DTaP.