Scientists with USDA’s Agriculture Research Service Monday announced that a vaccine candidate for African swine fever passed an important safety test required for regulatory approval. The successful safety test moves the vaccine one step closer to commercial availability. The new results show that USDA’s vaccine candidate does not revert to its normal virulence, after being injected into swine. This “reversion to virulence” test is required to ensure that the vaccine’s weakened form of the ASF virus does not revert to its original state. The safety studies are necessary to gain approval for use in Vietnam and eventually in other countries around the world. However, future commercial use will depend on approval from the department of animal health within each requesting country. Further development will continue once the vaccine candidate receives regulatory approval from Vietnam. Although the virus is causing profound economic losses to the swine industry, there have not been any outbreaks in the United States.