Safety and immunogenicity of live attenuated hepatitis A virus vaccine (H2 strain) in humans.

A study was made in Neijiang City, Sichuan Province to observe the safety and immunogenicity of a live attenuated hepatitis A virus (HAV) vaccine (H2 strain). 3,031 children, aged 6 to 9 years, were injected subcutaneously with 10(6.0) TCID50, 10(5.5) TCID50, and 10(5.0) TCID50 of HAV vaccine; the seroconversion rate and antibody GMT were 97.52%-90.68%, GMT = 1:5.19 +/- 1.90-1:3.36 +/- 1.94; 84.75%-76.27%, GMT = 1:4.29 +/- 1.96-1:2.0 +/- 2.67; 53.23%-51.61%, GMT = 1:2.57 +/- 1.89-1:1.68 +/- 1.41 respectively after 4 weeks to 12 months of inoculation. Forty-eight children in the control group were anti-HAV negative at 4, 8, and 12 weeks; 21 children in the oral group were not antibody positive 4 and 8 weeks after oral administration of the vaccine. The stool specimens of 3 of the 14 vaccinated children were HAA positive. The results suggest that the live attenuated HAV vaccine (H2 strain) is of good immunogenicity and safety.