In the individually randomized trial, one hepatitis A case was found in H2 vaccine recipients (3.6 per 100?000) vs. of 150 million doses of the live vaccines to children had led to a 90% reduction in the annual national incidence rate of hepatitis A in China during the 16-year period, from 1991 to 2006. Hepatitis A (HA) immunization with both live and inactivated HA vaccines was implemented in the national routine childhood immunization program in 2008 and around 92% of the 16 million annual births received the affordable live, attenuated vaccines at 18 months of age. Near elimination of the disease was achieved in a county of China for 14 years following introduction of the H2 live vaccine into the Expanded Immunization Program (EPI) in 1992. monkeys by intravenous (iv) injection, did not cause elevated liver enzyme activity or any pathologic change in the liver, yet it induced immune responses in 43 animals (96%).12 When injected iv into 11 marmosets ( 0.01 ; comparison of anti-HAV positivity between Group C and D: 2 = 5.10, 0.05. The immune responses to a single vaccine dose were similar between H2 (106.82TCID50) and LA-1 strain (106.75TCID50) recipients (Table 2). The anti-HAV sero-positive rate in H2 vaccine group dropped from 92% with GMT of 126 mili-international unit per mililiter (mIU/mL) at 3 mo to 75% with GMT of 81 mIU/mL at 36 mo as measured by Abbott IMx system, the detection level of which was around 30 mIU/mL 30 (Table 2). The rate was 71.6% with a GMT of 89 mIU/mL at 8 y.30 Thus, the antibody decline was quite slow over the 8-y period. The Chinese inactivated HAV vaccine (Healive) in 2 doses caused much higher antibody level; it induced 100% sero-conversion with a GMT of 3237C3814 mIU/mL at 7 mo after the first dose or 1 mo after the second Vatiquinone dose.31 On the other hand, cellular immune responses were observed in humans immunized with the live attenuated vaccine.32 Therefore, persistence of the immune responses to the live vaccines, in comparison with those to the inactivated HA vaccine, requires further studies. The lower limit of anti-HAV needed for protection of hepatitis A, has not been determined. Studies of an inactivated HAV vaccine, VAQTA, have used anti-HAV concentration of 10 mIU/mL as protective level.33 Obviously, Merck Company that sponsored the VAQTA project, developed more sensitive anti-HAV assay for their vaccine studies. Table?2. Anti-HAV# in recipients of LA-1 and H2 vaccines during 3 y follow-up+ Month*LA-1 Vaccine Group?????????????????H2 Vaccine Group= 0.07).26 Field Evaluation of Protective Efficacy of the Vaccines Efficacy trial of the low-dose vaccine in a single dose In the C10rf4 first efficacy trial, a single dose of 105.50TCID50 given subcutaneously, Vatiquinone was evaluated. A total of 54 746 children, 6C9 y old, were randomized to H2 vaccine, LA-1 vaccine or the control group.34 Month of birth was used for the randomization. The control group did not receive the live HA vaccine until the follow-up study was completed. The children were not tested for susceptibility before the vaccination. Sero-prevalence of anti-HAV in a sample of Vatiquinone the study population before the trial was 22.3% (1079/4837). The existing surveillance system for infectious diseases was used for follow up. Local clinicians were trained to report suspected acute hepatitis cases, fill out the forms of case report, and collect serum Vatiquinone specimens for laboratory diagnosis. Local CDC people visited the hospitals for monitoring case-finding and specimens collection. They also visited schools regularly, found suspected patients among absentees, and collected serum specimens from them. All specimens were tested for IgM anti- HAV at the central laboratory; those with positive test, elevated ALT and clinical symptoms of hepatitis were defined as HA cases. No severe adverse event was reported. Sero-conversion at 3 mo of vaccination, measured with modified HAVAB,15,16 was 36.3% for H2 vaccine group and 35.3% for LA-1 vaccine group. During the 17-mo follow-up period after the 18 d of the vaccination, 5 hepatitis A cases were reported in 17?733 subjects of H2 vaccine group (2.82 per 10?000), 6 in 18?397 of LA-1 vaccine group (3.26 per 10?000) vs. 22 in 18?616 of control group (11.82 per 10?000). The differences in the incidence rates between each of the 2 vaccine.