This document relates to methods and materials for making and using viruses (e.g., measles viruses or adenoviruses) having a reduced susceptibility to antibody neutralization (e.g., antibody neutralization by serum from measles virus vaccines). For example, recombinant morbilliviruses (e.g., recombinant measles viruses) having a modified H gene and a modified F gene, as well as methods of using a recombinant virus are provided.