Philip Felgner and Huw Davies with the Department of Medicine at the University of California, Irvine, found the modified vaccinia virus Ankara produced the same antiviral response in human and animal studies as the current smallpox vaccine, Dryvax, the university said Monday in a release.

The findings are published in the Journal of Virology.

Smallpox was declared eradicated worldwide in 1980. Routine vaccination against smallpox in the United States stopped in 1972.

Dryvax was effective during the eradication campaign but its manufacturing methods are outdated by today's standards and vaccine is associated with significant risk of adverse reactions, the report said.

Felgner and Davies said serum antibody responses were similar in both animal and human subjects regardless whether they were given the modified vaccine or Dryvax, suggesting the new vaccine contains antiviral properties similar to those in Dryvax.