The present invention provides for modified Flavivirus such as a modified Zika virus. The modification according to various aspects of the invention results in reduced viral proteins compared to a parent virus, wherein the reduction in expression is the result of recoding one or more regions of the virus. For example, the prM, or envelope (E) region, or the nonstructural protein 3 (NS3) region or both the E and NS3 regions can be recoded. In various embodiments one or more regions are recoded by reducing the codon pair bias or codon usage bias of the protein-encoding sequence. These modified Flavivirus are used as vaccine compositions to provide a protective immune response.
