Abstract: ObjectiveTo increase the crow d immune standard and to decrease the morbidity of hepatitis A after a mass vaccination of live attenuated hepatitis Avaccine.MethodsIt was surveyed in the positive rates of anti-HAV IgG and the morbidity of hepatitis A both in front of a mass vaccination and behind that to carry out the immune coverage of live attenuated hepatitis A vaccine for the suscept ible crow d of hepatitis A year by year.ResultsThe accumulative inoculation rates of live attenuated hepatit is Avaccine was 21.63% in 5 years from 1993 to 1998,among which they were 44.13% and 73.21% respectively in the preschool children,primary and middle school students.In 1998 the crowd positive rates of anti-HAV IgG was 74.24% and the morbidity of hepatit is A was decreased to 15.60/100 000.In hepatitis inspecting area of Dongtai.The positive rates of the antibodies was only 40.00% in 1989 and it increased to 62.25% in 1998.ConclusionIt could decrease the susceptible greatly and increase the immune standard of whole crowd to carry out a mass vaccination.If routine vaccination of live attenuated hepatitis A vaccine for the susceptible crowd was carr ied out,it could build the colony immune defence of hepatitis A step by step and it must effectively control the epidemic of hepatitis A.