We should not give up on developing a MLV vaccine for ASF.
In recent meetings with R&D leaders of domestic and international animal health companies in China, the topic of a modified live virus (MLV) vaccine for African Swine Fever (ASF) was often discussed. Most of these company leaders do not believe that an MLV vaccine will be approved by the Chinese regulatory agency anytime soon. The major concern is the safety of MLV vaccines.
The danger of an ASF MLV vaccine has been clearly demonstrated by the unauthorized introduction of various attenuated ASF viral strains as experimental vaccines in China in the last few years. These “less-virulent” MLV strains caused more damage than the wildtype ASFV because the disease became clinical when pigs grew older and were stressed.
However, we should not give up the hope that a safe and efficacious MLV vaccine for ASF is possible. Afterall, the safe and efficacious C-strain Classical Swine Fever (CSF) vaccine is an MLV vaccine and it has been successfully used to control CSF in many countries in the last few decades. Because MLV vaccines are often administered once and are more efficacious (quicker onset of immunity and longer protection) than subunit vaccines, they are usually a more cost-effective tool for infectious disease prevention and control compared to other types of vaccines. If an MLV ASF vaccine has a similar level of safety and efficacy profile as the C-strain CSF vaccine for CSF, it should be approved for use in ASF control and prevention.