RESUMO
OBJECTIVE: To compare the antibody level of vaccine group and control group in a randomized, controlled trial of type B inactivated vaccine against hemorrhagic fever with renal syndrome(HFRS) in Jiande County of Zhejiang Province and to find out if there is enhancement of subclinical infection about type B inactivated vaccine against HFRS. METHODS: The number of sera collected (July 1994-July 1998) in vaccine group immunized type B inactivated vaccine against HFRS and control group were 305 and 283 persons in Jiande County respectively, and indirect immunofluorescent antibody method(IFAT) was used for testing the titer of HFRS IgG in sera. The cut-off values were determined on IFA titer of the second sera in control group with positive and negative IFA before vaccine was given respectively, and the subclinical infection of positive and negative IFA of the first sera in vaccine group was evaluated. RESULTS: When taking different cut-off values of subclinical infection, there were no statistical differences in HFRS IFA positive rates between vaccine group and control group of positive IFA in the first sera. In vaccine group and control group of negative IFA before vaccine given, also the IFA positive rates were not statistically different in these groups. There were no statistical differences of IFA GMT and IFA sero-negative rate between vaccine group and control group. CONCLUSIONS: The investigation showed there was no statistical difference in antibody level between vaccine group and control group, so there could not be enhancement of subclinical infection of vaccine group receiving type B inactivated vaccine against HFRS.
