Systemically administered DNA and fowlpox recombinants expressing four vaccinia virus genes although immunogenic do not protect mice against the highly pathogenic IHD-J vaccinia strain.

Highlights: [•] Effective smallpox vaccine is still required against deliberate variola release. [•] DNA/FP recombinants against OPXV might represent a safe prime-boost strategy. [•] New avipoxvirus-based recombinants might improve vaccine immunogenicity. [•] Fowlpox-based recombinants can be used in VV-experienced humans. [•] Presence of neutralizing antibodies does not always correlate with protection. [Copyright &y& Elsevier]