[Study on the effects of controlling hepatitis A epidemics by building the colony immune defence].

OBJECTIVE: To build the colony immune defence and to control the periodic epidemics of hepatitis A after a mass vaccination of live attenuated hepatitis A vaccine. METHODS: Through yearly observing the correlation of the accumulative inoculation rates of live attenuated hepatitis A vaccine, the crowd immune standard and the morbidity of hepatitis A after administered live attenuated hepatitis A vaccine among susceptible population and surveilling anti-HAV IgG in the different epidemic areas. RESULTS: (1) The accumulative inoculation rates of live attenuated hepatitis A vaccine was 34.15% in 8 years from 1993 to 2000, among which they were 84.46%, 82.23% and 15.14% in the preschool children, primary and middle school student and 15 - 45 age groups respectively. The morbidity of hepatitis A decreased to 8.26/100,000 in 2000. (2) The crowd positive rates of anti-HAV IgG were 74.24% in 1998 and 83.68% by 2000. Among which they were 74.02%, 68.49%, 79.41%, 85.71% and 90.80% in 2 - 4, 6 - 8, 13 - 15, 20- and 30 - 39 age groups respectively. (3) The accumulative inoculation rates were 37.36%, 51.08% and 28.68% in the inspection areas of Tongtai, Binhai and Yandu respectively. The crowd positive rates of anti-HAV IgG in three inspect area were 85.71%, 85.94% and 78.63% respectively. It was noticed the correlation between the accumulative inoculation rates and the crowd positive rates of anti-HAV IgG was (r(city) = 0.91, F = 15.10, P < 0.03). CONCLUSION: The results showed that the crowd positive rates of anti-HAV IgG had increased to 85% while, the colony immune defence of hepatitis A was effectively built to break the periodic epidemics of hepatitis A. The morbidity of hepatitis A decreased to the lowest level in the history.