African swine fever vaccine candidate moves one step closer to market

The Agriculture Research Service (ARS) announced that one of its vaccine candidates for African swine fever (ASF) has hit a significant milestone on the path to commercial approval. The vaccine passed a federal safety inspection, an important step in a series of safety tests.

The results revealed that the candidate does not revert to its normal virulence after being injected into swine. This is a required test to demonstrate that the weakened form of the ASF virus does not return to its original state.

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"It is very hard to predict how selective pressure can cause a live attenuated vaccine to return to virulence," says senior ARS scientist Douglas Gladue. "In the case of this particular vaccine candidate, we deleted a gene, which makes it difficult for the virus to simply add the gene back. So, we expected reversion to its original form to be unlikely, but the test still had to be performed."

Vaccine strains keep most of their original genetic makeup and could potentially change when exposed to environmental variables, which is why safety tests like these are performed.

These studies are necessary to gain approval for use in Vietnam and eventually in other countries around the world. Commercial use in the future will hinge on individual safety standards determined by an individual country. The vaccine candidate was recently selected by NAVETCO for commercial development in Vietnam. Further development of the candidate will continue once the vaccine gets approval in Vietnam.

Though the risk of ASF poses a significant economic threat to the swine industry, there have not been any outbreaks in the United States. In 2007, cases spread from Africa and the Republic of Georgia, and several were reported in Central Europe, Asia, and the Dominican Republic in 2021.