  We show that a short-time regime, in which a deviation from the exponential
decay law occurs, exists also in the framework of a superrenormalizable
relativistic quantum field theory. This, in turn, implies the possibility of a
quantum Zeno effect also for elementary decays. The attention is then focused
on the typical order of magnitude of strong decay rates of mesons: for these
particles, strong deviations from the exponential decay law are present during
a period of time comparable with their mean life time. As a concrete example,
the case of the $\rho $ meson is studied.
