Hope and hurdles: unlocking the potential of modified live virus vaccines for African swine fever

African swine fever (ASF), caused by the African swine fever virus (ASFV), poses a serious threat to the global swine industry, causing substantial economic losses and raising significant concerns for food security. The virus' s complex pathogenesis and our limited understanding of its immune evasion mechanisms remain major obstacles to vaccine development. Among current strategies being pursued, modified live virus (MLV) vaccines, despite ongoing safety concerns, have shown the greatest potential to elicit protective immunity. Currently, MLV vaccines are the only ASFV vaccines approved for commercial use. This review summarizes recent advances in ASF MLV research, with a focus on the effects of gene-deleted MLVs on protective efficacy and safety, and provides a comprehensive catalog of all currently identified single-gene and multi-gene targets. Finally, it discusses the key technical, safety, and regulatory challenges that must be addressed to facilitate the development and deployment of ASF MLV vaccines.