COMBINED VACCINATION AGAINST YELLOW-FEVER AND TYPHOID-FEVER - A COMPARATIVE TRIAL

In order to evaluate a combination of yellow fever and typhoid fever v accine, we conducted a controlled trial comparing reactogenicity and i mmunogenicity of Vi polysaccharide (ViPS) vaccine and yellow fever 17D (YF) vaccine after single, simultaneous and combined administration. The combined YF/ViPS vaccine was prepared by using the liquid ViPS vac cine as a diluent for the YF vaccine. The stability of such a reconsti tution had been assessed in vitro. Safety was evaluated using a self-s urveillance form and by repeated clinical visits. Immunogenicity was e valuated by a plaque reduction test for YF and by radioimmunoassay for ViPS. Tolerability was satisfactory in all groups. There was no incre ase in local or general reactions in groups receiving both vaccines, w hether given simultaneously or combined. The serological response to V iPS was similar after single and simultaneous or combined administrati on. Interestingly, the immune response to YF was significantly enhance d in groups receiving the vaccines simultaneously or combined, suggest ing a potential adjuvant effect of ViPS.