Live Attenuated Vaccines for African Swine Fever: Perspectives on Their Use and Strategic Directions

Abstract

African swine fever (ASF) continues to cause substantial economic and production losses in affected countries. Although biosecurity and conventional control measures remain essential, the challenges of ASF control underscore the need for safe and effective vaccines as additional tools, particularly in endemic settings. Live attenuated vaccines (LAVs) are the most advanced ASF vaccine platform, providing the most consistent protection to date and remaining the only ASF vaccines to reach commercial deployment. Field experience with licensed products has shown encouraging safety, immunogenicity, and disease-control outcomes. However, the introduction and spread of recombinant genotype I/II strains may reduce vaccine effectiveness and contribute to limited vaccine uptake. Together with the detection of vaccine-like variants of uncertain origin, these issues have generated contrasting perspectives: a precautionary view focused on risks associated with replication-competent vaccine viruses, and a benefit–risk view emphasizing the consequences of continued ASFV circulation without effective vaccination. This review contrasts these perspectives, draws lessons from other live vaccines, and frames the responsible use of ASF LAVs within a benefit–risk approach. Experience with human and veterinary LAVs shows that persistence, transmission, genetic instability, reversion to virulence, and recombination are inherent biosafety concerns of LAVs, yet such vaccines remain important when alternative platforms do not provide equivalent protection. Their use therefore requires identifying, monitoring and minimizing residual risks in relation to expected benefits. Accordingly, ASF LAVs should be avoided in ASF-free regions but may be justified in endemic settings when licensed products are used within coordinated programs integrating adequate coverage, biosecurity, surveillance, and molecular monitoring. Future vaccine development should focus on improving safety in growing pigs and breeding animals, broadening protection against emerging ASFV strains, validating DIVA tools and developing safer next-generation platforms, while continued reassessment ensures that vaccine use remains appropriate to epidemiological conditions, emerging evidence, and disease-control needs.