Provided herein are recombinant poxviruses that are stable through successive passaging of the recombinant poxviruses. More particularly, the recombinant poxviruses comprise one or more modified nucleic acids encoding MUC1, CEA, and/or TRICOM antigens, wherein the recombinant poxviruses are stable through successive passaging. Also, provided herein are compositions and method related thereto.