Japanese encephalitis vaccine (inactivated, BIKEN) in US soldiers: Immunogenicity and safety of vaccine administered in two dosing regimens

The safety and immunogenicity of Japanese encephalitis (JE) vaccine (Nakaya ma strain, monovalent / BIKEN) was studied in 538 U.S. soldiers in 1990. Th ree doses of vaccine from three consecutively manufactured lots were given on days 0, 7, and either 14 or 30. Serum for antibody determination was dra wn at months 0, 2, and 6. Japanese encephalitis plaque reduction neutraliza tion tests were pel formed by three laboratories on each specimen. Five hun dred twenty-eight (98%) participants completed the immunization series. All recipients without antibody before immunization developed neutralizing ant ibody against JE virus. There were no differences in geometric mean titer a mong the three test lots at months 2 and 6. Soldiers who received the third dose on day 30 had higher titers at both time points. Antibody to yellow f ever had no significant effect on immune response to vaccine. Conclusions d rawn from analysis of serologic data from the three labs were nearly identi cal. Symptoms were generally limited to mild local effects and were reduced in frequency with each subsequent does in the series (21% to 11%; P < 0.00 01). Generalized symptoms were rare (e.g., fever = 5%) with no reported cas es of anaphylaxis.