Observation of Epidemiological Effectivity of Standardized Live Attenuated Hepatitis A Vaccine(LA-1 strain)

For evaluating the epidemiological effictivity of live attenuated hepatitis A vaccine(LA-strain),in Dec 1996,76,000 children of 1～12 years old in Liucheng county of Guangxi Zhuangzu Autonomous Region were enrolled in this study and they were randomly divided into 3 groups(the vaccine group?the control group and the external group, according to the months they were born.Children in the vaccine group were given one dose of 10 6 5 TCID 50 /ml live attenuated hepatitis A vaccine,those in the external group were given one dose of Vi polysaccharide typhoid vaccine and in the control group were given nothing In the 5 years of follow up,there were 38 hepatitis A cases found in the control group and the external group, the incidence was 62 79 per 100,000 population There was only one hepatitis A case in the vaccine group and the incidence was 6 34 per 100,000 population The difference of the incidence between the vaccine group and the control groups was highly significant(P0 05) The protective efficacy of the vaccine was 89 90%(95%CI:69 86%～100 00%) We concluded that giving one dose(10 6 5 TCID 50 /ml)of standardized attenuated live hepatitis A vaccine(LA-strain),the epidemiological effictivity after 5 years was good.