Primary humoral immune responses to formalin inactivated hemorrhagic feverwith renal syndrome vaccine (Hantavax (R)): Consideration of active immunization in South Korea

The efficacy of a formalin-inactivated hemorrhagic fever with renal syndrom e (HFRS) vaccine and the effectiveness of a related vaccination program hav e not been previously evaluated. We measured the primary immune responses t o Hantavax((R)) by plaque reduction neutralizing antibody test (PRNT), var hemagglutination inhibition test (HAI), ELISA and high density particle agg lutination test (HDPA) in order to confirm a possible, biological efficacy through independent substantiation of experimental results and to compare t he results with previous studies. Following two doses of primary vaccinatio n, the seroconversion rate of PRNT and HAI antibody was 39.3% (10/30)[95% C .I. 17.3-52.5%] and 26.7% (8/30) [95% C.I. 12.3-45.9%], respectively. The c orrelation between PRNT and HAI antibody showed a statistical significance (r=0.58, pc 0.01). The seroconversion rate of HDPA and ELISA were both 76.7 % (23/30) [95% C.I. 57.7-90.1%], which correlated well with each other (r=0 .58, p <0.02). In our study, Hantavax((R)) elicited low neutralizing antibo dy responses, at least in the volunteers samples that we tested. The vaccin ation program, including the vaccine: itself, that has been adopted by the national immunization program to protect against HFRS in Korea should be re -evaluated and re-formulated to produce a higher protective immune response rate.