Background: African swine fever virus (ASFV) continues to spread globally, causing severe economic losses to pig farmers. Vietnam licensed two live attenuated vaccines based on the ASFV strains ASFV-G-ΔI177L and ASFV-G-ΔMGF to control the ongoing ASF outbreaks. In 2023, newly emerging highly virulent recombinant ASF viruses (rASFV I/II) containing genetic elements from both p72 genotype I and II ASF viruses were reported from Northern Vietnam. Objective: This study evaluated whether the two vaccine strains were able to protect the pigs against the emerging rASFV I/II strain VNUA/rASFV/TN1/23. Results: Pigs vaccinated with ASFV-G-ΔMGF or ASFV-G-ΔI177L, when challenged with rASFV I/II, succumbed to the infection, or developed signs of chronic ASF. Conclusions: The findings from this study show that both vaccine strains that are licensed and used in Vietnam are unlikely to protect pigs from the emerging highly virulent rASFV I/II. This complicates the ongoing efforts to control ASF in Asia and globally and emphasizes the urgent need for a novel vaccine that can effectively protect pigs from the rASFV I/II.

African swine fever (ASF) is one of the most devastating diseases affecting the global pig industry. Therefore, the development of safe and effective vaccines is crucial in combating the virus. The AVAC ASF LIVE vaccine, produced from an attenuated genotype II ASF virus (ASFV) strain with the deletion of six MGF genes and cultured in a Diep’s macrophage (DMAC) cell line, has been officially licensed for use and commercialization in Vietnam. This study evaluated the safety and efficacy of the AVAC ASF LIVE vaccine. In the safety experiment, pigs received a dose equivalent to 100 times the protective dose. In the efficacy experiment, control pigs and one‐dose vaccinated pigs were challenged with a highly virulent p72 genotype II ASFV on day 28 post‐vaccination. The duration of protective immunity was assessed by challenging pigs at various time points, from 2 weeks up to 6 months post‐vaccination. Results showed that pigs given the 100‐fold protective dose remained healthy with no abnormal signs. Significantly, 60% of vaccinated pigs survived the challenge 14 days after vaccination, and the survival rates reached 100% when challenged at 28, 90, 120, and 150 days post‐vaccination (dpv). The vaccine effectively induced robust immunity, leading to a reduction in viral shedding and the persistence of viral DNA in vaccinated animals. In conclusion, the AVAC ASF LIVE vaccine has demonstrated safety and high efficacy in protecting pigs from genotype II ASFV infection.

African swine fever virus (ASFV) continues to spread globally causing severe economic losses to the pig farmers. Vietnam licensed two live attenuated vaccines based on the ASFV strains ASFV-G-ΔI177L and ASFV-G-ΔMGF, to control the ongoing ASF outbreaks. In 2023, newly emerging highly virulent recombinant ASFV viruses containing genetic elements from both ASFV p72 genotype I and II (rASFV I/II) strains were reported from Northern Vietnam. This study evaluated if the two vaccine strains were able to protect the pigs against the emerging rASFV I/II strain VNUA/rASFV/TN1/23. Pigs vaccinated with ASFV-G-ΔMGF or ASFV-G-ΔI177L, when challenged with rASFV I/II, succumbed to the infection, or developed signs of chronic ASF. The findings from this study show that both vaccine strains that are licensed and used in Vietnam, are unlikely to protect pigs from the emerging highly virulent rASFV I/II strains. This complicates the ongoing efforts to control ASF in Asia and globally and emphasizes the urgent need for a novel vaccine that can effectively protect pigs from the rASFV I/II strains.

African swine fever is a highly contagious and devastating disease of pigs. Here, we present the draft genome assemblies of three Vietnamese African s wine fever virus (ASFV) isolates: rASF1/2-avac02, rASF1/2-avac03, and rASF1/2-avac07. All isolates were closely related to the Chinese recombinant ASFV strains of genotypes I and II.