An immunogenic flavivirus composition comprising (i) a nucleic acid chimera comprising a first nucleotide sequence encoding nonstructural proteins and a capsid protein from a dengue-2 virus, wherein the C protein does not include the C-terminal signal peptide of the dengue-2 C protein, and a second nucleotide sequence encoding the C-terminal signal peptide of the C protein, a premembrane (prM) protein and an envelope protein from a West Nile virus, or; (ii) a first nucleic acid comprising a nucleotide sequence encoding an attenuated Dengue-2 virus strain PDK53; a second nucleic acid comprising a nucleotide sequence encoding nonstructural proteins and a capsid protein from an attenuated Dengue-2 virus strain PDK53 and a nucleotide sequence encoding premembrane (prM) and envelope proteins from Dengue-1 virus or comprising a nucleotide sequence encoding nonstructural proteins from an attenuated Dengue-2 virus strain PDK53 and a nucleotide sequence encoding C, prM and E proteins from Dengue-1 virus; a third nucleic acid comprising a nucleotide sequence encoding nonstructural proteins and a C protein from an attenuated Dengue-2 virus strain PDK53 and a nucleotide sequence encoding prM and E proteins from Dengue-3 virus, wherein the E protein contains a leucine at amino acid position 345; and a fourth nucleic acid comprising a nucleotide sequence encoding nonstructural proteins and a C protein from an attenuated Dengue-2 virus strain PDK53 and a nucleotide sequence encoding prM and E protein from Dengue-4 virus, wherein the E protein contains a leucine at amino acid position 447 and wherein the C protein contains a serine at position 100; wherein the immunogenic composition comprises a pharmaceutically acceptable carrier or vehicle, or an adjuvant. (i) a nucleic acid chimera comprising a first nucleotide sequence encoding nonstructural proteins and a capsid protein from a dengue-2 virus, wherein the C protein does not include the C-terminal signal peptide of the dengue-2 C protein, and a second nucleotide sequence encoding the C-terminal signal peptide of the C protein, a premembrane (prM) protein and an envelope protein from a West Nile virus, or; (ii) a first nucleic acid comprising a nucleotide sequence encoding an attenuated Dengue-2 virus strain PDK53; a second nucleic acid comprising a nucleotide sequence encoding nonstructural proteins and a capsid protein from an attenuated Dengue-2 virus strain PDK53 and a nucleotide sequence encoding premembrane (prM) and envelope proteins from Dengue-1 virus or comprising a nucleotide sequence encoding nonstructural proteins from an attenuated Dengue-2 virus strain PDK53 and a nucleotide sequence encoding C, prM and E proteins from Dengue-1 virus; a third nucleic acid comprising a nucleotide sequence encoding nonstructural proteins and a C protein from an attenuated Dengue-2 virus strain PDK53 and a nucleotide sequence encoding prM and E proteins from Dengue-3 virus, wherein the E protein contains a leucine at amino acid position 345; and a fourth nucleic acid comprising a nucleotide sequence encoding nonstructural proteins and a C protein from an attenuated Dengue-2 virus strain PDK53 and a nucleotide sequence encoding prM and E protein from Dengue-4 virus, wherein the E protein contains a leucine at amino acid position 447 and wherein the C protein contains a serine at position 100; wherein the immunogenic composition comprises a pharmaceutically acceptable carrier or vehicle, or an adjuvant.