Regarding single dose Hepatitis A vaccine:
The international vaccine was first developed by Dr Mao, the main inventor of the vaccine in the year 1987 and introduced in China in 1992. Till date over 120 million people have been administered the vaccine successfully in China.
There have been several studies of this vaccine in China. Seroconversion in follow-up assay 2 months and 10 years after inoculation was 98.6% and 80.2% respectively in a study done by ZHUANG Fang-cheng et al in China in 220 children. (Ref: Chinese Medical Journal, 2005, Vol. 118 No. 22 : 1851-1856). IN another study in 117 children, the immune response has been found to be comparable with other vaccines. (ref: Immune responses of anti-HAV in children vaccinated with live attenuated and inactivated hepatitis A vaccines. Vaccine. 2004 May 7;22(15-16):1941-5.)