Evaluation Of The Long-Term Epidemiological Effect Of Integrated Intervention Model Mainly By Vaccine To HFRS

Hemorrhagic fever with renal syndrome(HFRS)is a rodent-borne zoonosis caused by different species of Hantavirus(HV).It is a worldwide epidemic plaguing in many counties.China is the country most seriously affected by HFRS,and the number of the cases accounts for 90%of the total reported cases in the world.As the first case was reported in China,a lot of epidemical studies were carried on.They mainly identified the etiologic agents,host animals and the epidemic character of the HFRS.And also some of the interventions was put into practice.Among the measures,vaccination was initiated by the Chinese government as a national immunization programme to prevent and control the HFRS.However most of the researches focused on short or midterm immunological and epidemiological effects and few studies considered the long-term epidemiological effect of the vaccines.Furthermore,although the vaccines have been in use since approval and millions of doses have been given,the schedule of the vaccine continues to be debated.Thus,we conducted this study to assess the long-term epidemiological effectiveness of the Hantavirus vaccines and to optimize the vaccine schedule using an 11-year follow-up study.Junan County is one of primarily wild-rate type epidemic foci and of most prevalent regions for HFRS in Shandong Province,and it is also one of monitoring sites for HFRS in our country.So we selected Junan county as the trial field to conduct this study.Experimental epidemiological methods and integrated intervention model was used,which are mainly utilized to immune residents, and we evaluate its long-term epidemical effects of integrated vaccine intervention model and discuss the vaccine schedule.This research will be helpful for institution of scientific vaccine strategy and its application.Results from this study showed that:1.During the intervention period,the total rodent density and rodent Density of kinds in Junan County dropped significantly and were all controlled less than 4%.The rates of HFRS virus carriers were all bellow 6%.The indexes of HFRS virus carriers were also controlled below 0.04%.Contrast with the years before intervention,the rate of HFRS virus carries and the index of HFRS virus carries were both decreased.The annual incidence rate has shown an evident downward tendancy in Junan County and the number of the affected villages has been dropped.The incidence density after intervention was significantly lower than that of before.The total protective rate was 65.27%(95%CI:64.03～66.50),and the index of the effectiveness was 13.54(95%CI: 6.41～28.57).It indicated epidemic situation was controlled effectively by the integrated vaccine intervention.2.The cohort study show:Total incidence density of the vaccination group was 0.48 per 100000(95%CI:0.12 to 0.83),whereas that of the control group was 6.46 per 100000(95%CI:5.84 to 7.08).There was a significant difference in the incidence density between two groups and the former was much lower than the latter.It confirmed it was long-term effective in large scale populations by vaccination.3.We found that the immune programme of three doses without a booster was epidemiologically effective,with a protective rate of 100.00%based on the incidence density in the 11th year after vaccination and 92.62%based on the cumulative incidence rate over the whole study period.A booster might not be indicated for the primary three-dose SEO vaccine immunization for at least 11 years in a large population. Conclusions:1.The integrated control model was effective to prevent and control of HFRS in Junan County by the integrated vaccine intervention.2.After intervention,the population structure of host rodents and index of HFRS carrier have changed in residential areas.These changes may influence the feathers of the epidemic focus.3.The cohort study by 11 yeasr follow up showed that it was long-term effective in large scale populations by vaccination.4.We found that the immune programme of three doses without a booster was epidemiologically effective.A booster might not be indicated for the primary three-dose SEO vaccine immunization for at least 11 years in a large population.