Immunogenicity and protective efficacy of the current inactivated Japaneseencephalitis vaccine against different Japanese encephalitis virus strains

Mouse brain-derived, inactivated Japanese encephalitis (JE) vaccine has bee n internationally used for many years. It is believed that this vaccine mad e a great contribution to the reduction of JE patients in several countries . Mouse brain-derived, Beijing-1 and Nakayama JE vaccines induct: high leve ls of neutralizing antibodies. High levels of induced antibodies are mainta ined at least for 3-4 yr. The induced antibodies are cross-reactive to hete rologous strains; however, the neutralizing antibody titers against heterol ogous strains are usually lower than those against homologous strains. Cons idering that both Nakayama and Beijing-1 JE vaccines showed high levels of protective efficacy in Taiwan and Thailand where strains other than Nakayam a and Beijing-1 were circulating, we conclude that the current inactivated JE vaccine can induce high levels of protective immunity against heterologo us JE virus strains. (C) 2000 Elsevier Science Ltd. All rights reserved.