Abstract: The trial fields observation on epidemiological efficacy of three kinds of inactivated vaccines against HFRS(type I vaccines purified from tissue culture of Mogolian gerbils bidney;type I vaccines purifid from tissue cluture of mouse brains;type II vaccines prepared from tissue culture of hamster kidney) was carried out in the periods of eighth-five and ninth-five years national medical scientific studies,also the immunological strategy of these vaccines was suggested.The fields following up and expriment testing was cooperated when vaccine groups and control groups were allocated with cluser sampling.Four kinds of antibody testing methods of IFAT,MCPENT,ELISA and HI were operated for evaluating vaccines antibody reaction.The three kinds of vaccines were all safe and the moderate and svere side effects of vaccines were 0.56%,1.57%,3.26% for Mongolian gerbils kidney vaccine,mouse brains vaccine,hamster kidney vaccine respectively.The antibody-depdendent enhancement did not found in 143581 persons received vaccines aftver four years,also there were on statistically differences in clinical manifestations between 17 HFRS cases in vaccine group and 362 HFRS cases in control group (P> 0.10).The 119 inoculated individuals didn t show any clinical symptom while had seroconversion or increase of IFAT antibody titer which could be defined as second infection.The MCPENT and IFAT antibody reactions of three kinds of vaccine were good after 14 days,one year,two years,three years,four years of vaccine received.The seroconversion rates of MCPENT were 57.81% and 70.71%,51.09% and 61.90%,82.46% and 80.13% for Mongolian gerbils kidney vaccine,mouse brains vaccine,hamster kidney vaccine after 14 days of three doses of injection and one year reinforced respectively.The seroconversion rates of IFAT were 93.69% and 89.04%,84.27% and 83.05%,65.73% and 85.00% Mongolian gerbils kidney vaccine,mouse brains vaccine,hamster kidney vaccine after 14 days of three doses of injection and one year reinforced respectively.The change pheno menon of IFAT and MCPENT antibody was similar.The protection rates in trial fields were 93.77%,94.30%,97.61% for Mongoian gerbils kidney vaccine,mouse brains vaccine,hamster kidney vaccine respectively in the four years of three doses,so these vaccines were good epidemio logical efficacy.The immunological strategy of these vaccines showed type I vaccine and type I vaccine against HFRS could be used in the mixed and type I endemic areas,in the mixed of main type I endemic areas respectively.These vaccines can protect HFRS clinical infection effectively in four years of trial fields followed up.The study showed the side effects was slight and epidemiological efficacy was satisfied about three kinds of inactivated vaccines against HFRS produced in China when people were received these vaccines in the high endemic area,so the vaccine could be common inoculated.The immuno logical strategy was suggested according to these research results and epidemiological character of HFRS incidence.