  The effect of vacuum fluctuations on the in-medium hadronic properties is
investigated using a chiral SU(3) model in the nonlinear realization. The
effect of the baryon Dirac sea is seen to modify hadronic properties and in
contrast to a calculation in mean field approximation it is seen to give rise
to a significant drop of the vector meson masses in hot and dense matter. This
effect is taken into account through the summation of baryonic tadpole diagrams
in the relativistic Hartree approximation (RHA), where the baryon self energy
is modified due to interactions with both the non-strange $(\sigma)$ and the
strange $(\zeta)$ scalar fields.
