Race Against Time: Scientists Scramble for African Swine Fever Vaccine as Outbreak Returns to Spain

The return of African Swine Fever (ASF) to Spain after a 31-year absence is raising alarm bells among animal health experts. The recent discovery of infected wild boar near Barcelona has triggered a renewed sense of urgency, with scientists warning that prevention is currently the only effective weapon against this devastating virus.

“This is one of the most lethal and cunning viruses we face, and we have no other option but prevention,” says Dr. Marisa Arias, a researcher at the Center for Research in Animal Health CISA-INIA of the Spanish National Research Council (CSIC). The virus, which causes severe internal bleeding in animals, can wipe out entire herds of pigs within days of entering a farm.

A Vaccine Remains Elusive

Despite decades of research, a viable and safe vaccine for ASF remains elusive. Immunologists and veterinarians agree that creating a vaccine is exceptionally challenging. The virus’s complex nature allows it to evade the host’s immune system, making traditional vaccine approaches ineffective.

“The main obstacle is finding the right balance between efficacy and safety,” explains José Ángel Barasona, lead researcher on the WildASF-VAX project at the Complutense University of Madrid. “If we aim for very high safety, we’ll have relatively reduced efficacy.” His team is exploring the use of live attenuated vaccines, which carry inherent risks of causing side effects or reverting to a virulent form.

Promising Research Underway

Several research initiatives are currently underway, primarily led by Spanish scientists, with significant funding from the European Union. The Vacdiva project, completed in December 2024 after a four-year run and a €10 million investment, yielded two promising vaccine prototypes. These prototypes demonstrated at least 80% efficacy against the European genotype II strain of the virus and virtually eliminated transmission to other animals.

“Now the challenge is to complete the final studies to meet the requirements of the European Medicines Agency for registration and eventual commercialization,” Dr. Arias notes. “That won’t happen in the short term, but it’s a significant step forward.”

Another project, led by the pharmaceutical company Hipra, is developing a novel vaccine with potentially differentiating characteristics. Hipra, known for its rapid development of a COVID-19 vaccine, is coordinating the Vax4ASF consortium, a European collaboration of 17 partners. Initial prototypes are slated for animal testing in 2026.

“Our goal is to develop a vaccine that can adapt to the demands of the European context,” says Marta Sitjà, Director of Animal Health R&D at Hipra.

Understanding Resistance: A Parallel Track

Beyond vaccine development, researchers are also investigating why certain African species, like the warthog, potamochero, and red river hog, appear resistant to ASF. A team at the Centre for Genomic Regulation (CRG) in Barcelona is collaborating with European groups to unravel the genetic mechanisms behind this natural resistance. Understanding these mechanisms could unlock new strategies for protecting domestic pigs.

“Comprehending this natural resistance will open the door to developing better tools to protect domestic pigs, whose vulnerability has already caused devastating economic losses worldwide,” researchers at the CRG state.

Global Impact and Economic Concerns

ASF poses a significant threat to the global pork industry. Outbreaks can lead to mass culling of animals, trade restrictions, and substantial economic losses. The Food and Agriculture Organization of the United Nations (FAO) estimates that ASF has caused billions of dollars in economic damage worldwide. The re-emergence in Spain underscores the need for continued vigilance and international collaboration to prevent further spread.

The race to develop an effective ASF vaccine is a critical undertaking, not only for the health of pig populations but also for the stability of the global food supply and the livelihoods of farmers worldwide.