Researchers push for region-tailored vaccines to combat African Swine Fever

KENYA – An international team of scientists has discovered that a promising African swine fever (ASF) vaccine candidate can protect pigs from some strains of the virus but offers little to no protection against others, underscoring the need for region-specific vaccines to combat one of the world’s most devastating livestock diseases.

The research, conducted by the U.S. Department of Agriculture’s (USDA) Plum Island Animal Disease Center in New York in collaboration with the International Livestock Research Institute (ILRI) in Nairobi, tested a commercial live-attenuated vaccine, ASFV-G-ΔI177L, against several strains of the virus collected from across Africa. Results revealed sharp differences in protection levels depending on the virus type.

A global animal health and economic threat

ASF is a highly contagious and often fatal disease that affects domestic pigs and wild boars. Despite decades of research, no globally approved commercial vaccine exists. 

The disease is endemic in many African countries, while recent outbreaks in Asia and Europe have devastated pig populations, wiping out millions of animals, disrupting pork supplies, and undermining rural livelihoods.

Smallholder farmers in low- and middle-income countries, who largely raise pigs in backyard systems, remain most vulnerable. Women and young people, who depend on pig farming as an income source, have been particularly affected. 

But the risks extend far beyond Africa. In the United States, the swine industry generated more than US$27 billion in gross cash receipts in 2023, while Canada’s pig sector contributed CAD 6.3 billion in 2024. Both economies face enormous exposure if ASF were to spread further.

Study reveals mixed protection outcomes

The vaccine candidate proved effective in some cases but fell short in others. Pigs that were vaccinated and exposed to the same strain used to develop the vaccine remained healthy, while unvaccinated pigs succumbed rapidly. 

Against a genetically different strain isolated in Ghana, about 80% of vaccinated pigs survived. However, the vaccine offered no protection against several other genetically distinct strains from Malawi, Kenya, South Africa, and Uganda, despite generating strong immune responses.

These results suggest that ASF viruses are too genetically diverse for a single vaccine to provide universal protection. Current methods of classifying ASF strains, based on a single gene known as p72- have also proved inadequate. In one case, two viruses with identical p72 sequences produced very different results in vaccinated pigs.

Rethinking vaccine strategies

To address this, USDA scientists have developed a new classification approach that examines the virus’s full set of protein-coding genes, offering a more precise way to match vaccines to regional virus types.

“Although much further corroborative experimental work is needed, the classification developed will likely be the only available rational approach for deciding vaccination procedures to control and manage ASFV outbreaks,” said Manuel Borca, USDA scientist.

ILRI’s Senior Scientist Anna Lacasta stressed that a new strategy is essential. “This research reinforces the need to rethink our ASF vaccine strategies. A one-size-fits-all solution is unlikely. We need targeted vaccines aligned with the regional virus biotypes to maximise protection and control outbreaks. There is need to support the development and licensing of vaccines based on circulating ASFV biotypes.”

The scientists recommend further research into matching vaccines to virus types, while also exploring new vaccine designs that could provide broader protection. 

For now, the findings mark a crucial step toward region-tailored ASF control measures that could help protect pigs, farmers, and economies worldwide.

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