Abstract:Four lots of HTN type HFRS vaccines and one lots of SEO type vaccine were used for human vaccination All lots of vaccine have passed the criterion of potency test except one lot of HTN vaccine Sera from vaccinated subjects were tested for neutralizing antibody response by micro-cytophathic neutralization The results have shown that those subjects vaccinated with vaccines which met the criterion of potency test developed good neutralizing antibody responses,the seroconversion rates 87%~100%,GMT 15~18,while those vaccinated with vaccine under criterion induced poor responses,sereoconversion rate only 60% and GMT 7 The results also revealed that the immune sera neutralized with vaccine homologous type virus strain were much better than with the heterologous type strain,seroconversion 100% vs 25% or 60% vs 20% It points out that quality control for the vaccine potency should be strict and bivalent vaccine of HNT and SEO needs to be developed in China