Protective efficacy of large-scale immunization with a live attenuated hepatitis A vaccine (LA-1 strain)

Objective To evaluate the long_term protective efficacy of large_ scale immunization with a standardized live attenuated hepatitis A vaccine (LA_1 strain).Methods A randomized controlled double blind study was conducted in 212 985 children between 1.5 and 10 years of age from 7 counties in Guangxi Province (100 735 in vaccine group and 112 250 in control group).Vaccine group was received one dose of HAV vaccine of 106.75 TCID50. Surveillance of the incidence of hepatitis A in two groups was started 1 month after vaccination. Results During a follow up of 36 months,71 cases of symptomatic HAV infection were found in the control and 2 in the vaccine group(63.25/106 vs. 1.99/106 respectively). The protective efficacy was estimated at 96.85% with 95% lower confidence limit of 92.4%. Conclusion It shows that a single standardized dose of live attenuated hepatitis A vaccine can come into being high and persistent protection against HAV.