  In this paper, an SIR epidemic model with variable size of population is
considered. We study optimal control problem for an SIR model with
"vaccination" and "treatment" as controls. It is shown that an optimal control
exists. We have already used functional, that lots of researchers use, and
found that this functional is not appropriate, it has a defect. Now, we fixed
this defect by changing this functional. We analyze the dependence of solutions
on parameter of problems and discuss our result.
