Studies on the duration of immune response against Japanese encephalitis virus from recipients with JE vaccine (Nakayama-NIH strain) in Korea.

To determinate the immune response and the duration of antibody against JE vaccine, 213 students were examined since 1994 using hemmaglutination inhibition test and plaque reduction neutralization test (PRNT).

24 months after the first vaccination, haemmaglutination inhibition and neutralizing antibody maintained from the recipients 63.4% (>1:20) and 100% (>1:20), respectively. In April 1996, one dose booster to the same recipients those who were vaccinated in 1994, the GMT antibody for HI and PRNT titer were both increased from 1:11.6 to 1:13.2 and 1:275.7 to 1:348.1, respectively, after 6 months booster (after 30 months from the initial vaccination). This results showed that the antibody from the active immunity could be maintained more than 12 months after the initial vaccination. On the basis of these results, inactivated killed JE vaccine (Nakayama-NIH strain) using for preventing against JE purpose seems to produce antibody enough to protect against JE at present .

Along with the results of this study demonstrating duration of antibody, the active immunization could be maintained as long as by initial vaccination of 2 doses, a single dose of booster vaccination made during a period of 1 month to 12 months and the successive booster vaccination by 2 or 3 year intervals. However, the immunization schedule should be concerned with both epidemiology of disease and the immune response of vaccinated individuals.