In the preceding two papers the author reported that the complement fixation reaction, by improvement of antigen, and the neutralization test and "Absättigungsversuch", by modifying its procedures, could be of use to some degree for the determination of the virus, and at the same time, could give an aid to the diagnosis of hepatitis. In the present paper the author makes reports on the antigenisity of the isolated strains and, moreover, on the immune-effect of vaccination: 1) The virus was inactivated by the addition of marzonin and preserving it in refrigerator over 3 weeks. Immunization of animals by this inactivated virus could protect them from the attack by the living virus. The fact that the infection-protection was established among the different strains suggested that the strains had no difference of antigenisity to one another but had unitary nature. 2) The modified "Absättigungsversuch" improved by the present author was serologically somewhat significant when the sera had a high titer, but was of little significance when the titer was low. It was suggested, however, that this method could be used as an aid for sero-reaction according to the purpose of tests.