ASSESSMENT OF NEUTRALIZING ANTIBODIES ELICITED BY A VACCINE (NAKAYAMA) STRAIN OF JAPANESE ENCEPHALITIS-VIRUS IN TAIWAN

A total of 368 blood specimens were resampled from a serum collection containing 2914 blood samples which were collected by a random samplin g in Taiwan In 1991. The plaque reduction neutralization test was appl ied to evaluate the neutralizing ability to two strains of Japanese en cephalitis viruses, i.e. Nakayama (the present vaccine strain) and JE5 (a Taiwan isolate). The result revealed that antibodies against JE vi rus were present in each stratified age group. Antibody positive rates were both highest in the group older than 70 years although the lowes t rates were located in different groups. In addition, the result show ed that the immunogenicity potency of the antibody induced by the vacc ine strain did not have a good coverage against JE5. The rate of neutr alizing antibodies above the level of protective efficacy of the prese nt vaccine was limited as low as 37.93 %. Efficacy of the vaccine used at present was apparently not efficient. Consideration of a more prom ising vaccine may be necessary.