Hantaan virus was serially passaged in the brains of suckling mice. Vaccine inactivated with formalin was prepared from the suckling mice brains and the antigenic potency of the vaccine was determined by enzyme-linked immunosorbent assay (ELISA).
Mice immunized with the vaccina were protected when challenged with live Hantaan virus. The vaccine(Hantavax) contained 1,024 ELISA units/0.1 ml of Hantaan virus antigen and 0.5 ml of vacine were given subcutaneously to a vaccinee. The antibody
responses and the duration of antibody persistence of 74 vaccinees given inactivated Hantaan virus vaccie 3 times at 0, 1 and 13 month after first vaccination against hemorrhaic fever with renal syndrome (HFRS) were then studied.
1. Seroconversion rate after vaccination was 89%, 97%, 81% and 37% at 1, 2, 6 and 13 month respectively.
2. Mean reciprocal titer of IgG antibody increased markedly to 274 after second dose, it decreased to 102 and 17 at 6 and 13 month respectively. After booster vaccination at 13 month, IgG titer increased again to 644. There was no sexual
difference
in
the seroconversion rate and the duration of antibody persistence.
3. In control group who antibody persistence.
4. A few vaccinees experienced side effects which were mild and tolerable.
It is suggested that booster vaccination 1 year after first dose of Hantavax would be necessary to maintain high level of antibody and effective immunity against Hantaan virus.
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