African Swine Fever (ASF) live-attenuated vaccines (LAVs) present multiple safety concerns, including virulence reversion, recombination, persistent viremia, and reproductive safety in gestating sows. The Vietnam's commercialization experience high light the need to re-evaluate the safety of gene-deleted LAVs. The magnitude and duration of viremia are key indicators of vaccine safety. Cases of fetal abnormalities, transplacental transmission, and virulence reversion following vaccination of pregnant sows underscore the limitations of clinical trials and the long-term, multi-generational risks associated with vaccine use. Accordingly, broad regulatory standards are required, covering safety in piglets and sows, horizontal transmission, virulence reversion, and environmental risks from living modified organisms (LMOs). The establishment of a molecular epidemiology-based post-marketing surveillance (PMS) system is needed. This system should include pre-introduction characterization of regional circulating strains, post-vaccination active surveillance, and whole-genome sequencing to monitor for mutations. A regulatory-scientific framework ensuring both safety and efficacy must be established through international collaboration and standardized reporting systems.

Abstract
INTRODUCTION
GENERAL SAFETY CONSIDERATIONSFOR LIVE VACCINES
    Virulence reversion
    Emergence of recombinant viruses
    Excessive attenuation
WOAH GUIDELINES FOR AFRICAN SWINEFEVER VACCINE
    Minimum requirements for African swine fever liveattenuatedvaccine (LAV)
    Considerations for vaccine development and licensing
    Characteristics and quality control standards of masterseed virus
    Safety and efficacy verification
    Licensing approval requirements (Table 1)
SAFETY ISSUES AFTER THE ASF VACCINELAUNCH IN VIETNAM
    Safety of commercial vaccines
    Safety in pregnant sows
    Genetic safety of vaccines
VIREMIA AS A SAFETY ASSESSMENT FACTOR
    Viremia and safety
    Correlation between viremia and virulence reversion
    Live-attenuated African swine fever vaccine andviremia
POST-MARKETING MEASURES TO ENSURECOMMERCIAL VACCINE SAFETY
    PMS for ASF LAVs
    Molecular biological post-marketing monitoring
CONCLUSION
ACKNOWLEDGEMENTS
REFERENCES

• Hyoungjoon Moon(Department of Animail Health and Welfare, College of Healthcare & Biotechnology, Semyung University, Jecheon 27136, Korea) Corresponding author