  By using an appropriate version of the synchronous SIR model, we studied the
effects of dilution and mobility on the critical immunization rate. We showed
that, by applying time-dependent Monte Carlo (MC) simulations at criticality,
and taking into account the optimization of the power law for the density of
infected individuals, the critical immunization necessary to block the epidemic
in two-dimensional lattices decreases as dilution increases with a logarithmic
dependence. On the other hand, the mobility minimizes such effects and the
critical immunizations is greater when the probability of movement of the
individuals increases.
