Studies on Safety and lmmunogenicity of Freeze-dried Live Attenuated Hepatitis A Vaccine (H_2 Strain)

To assess the safety and immunogenicity of freeze-dried live attenuated hepatitis A (HA) vaccine (H_2 strain) inoculated to humans, we chose 164 primary school students of 7-12 years old from Mengshan County of Guangxi Autonomous Region and 114 kindergarten children of 3-6 years old from Jiaojiang District of Taizhou city of Zhejiang Province. They were all anti-HAV-IgG negative, SGPT normal, no hepatitis history and no hepato-symptoms. These two groups of subjects were inoculated separately with two different batches of freeze-dried live attenuated HA vaccine H_2 strain, and then observed for systemic and local reactions 30min, 8, 24, 48, 72h after vaccination, their body temperatures and clinical reactions were recorded every other day. Their blood samples were collected 1 and 2 months after vaccination for anti-HAV-IgG and SGPT testing. When followed up as long as 13 and 24 months, anti-HAV-IgG was tested again by EIA competition inhibition assay marked by WHO standard sample (100mIU/ml). The results showed that during the whole period of observation, no medium and severe adverse effects or any clinical reactions were seen, no SGPT abnormality, suggesting that H_2 vaccine is safe. The positive seroconversion rates of this vaccine vaccinated after 2 months, 13-24 months were 99.1%～100% and 97.8%～98.9% respectively. The GMT after 2 months reached 1607mIU/ml and maintained at 448.3mIU/ml after 24 months, which was 4 times higher than that of the same domestic product 2 months after inoculation. The immunogenicity of freeze-dried live attenuated HA vaccine H_2 strain is satisfactory.