I think they mean the vaccine will be 100 times worse than the Covid vaccine.
Avian influenza (fowl plague) virus is not pathogenic for human. In other words , humans cannot develop disease due to the influenza virus. Humans can be infected by that virus and develop antibodies but the infection is asymptomatic .We do not know if the the infection in humans is an active infection or just a reactivity of the body when challenged with any antigen. There is one single case of death in human due to avian influenza documented in China several decades back. I could not find out how they “documented” the death due to the avian virus infection, in that case.