A vector comprising a first
DNA sequence which is complementary to at least part of an
alphavirus RNA genome and having the complement of complete
alphavirus DNA genome replication regions, a second
DNA sequence encoding a paramyxovirus
protein, particularly a respiratory syncytial
virus fusion (RSV F)
protein or a RSV
F protein fragment that generates antibodies that specifically react with RSV
F protein, the first and second DNA sequences being under the transcriptional control of a
promoter is described. Such vector may be used to produce an
RNA transcript which may be used to immunize a host, including a human host, to protect the host against
disease caused by paramyxovirus, particularly respiratory syncytial
virus, by administration to the host.