https://www.science.org/content/article/u-s-conditionally-approves-vaccine-protect-poultry-avian-flu
“Although many influenza researchers contend that vaccination can help control spread of the deadly virus, the U.S. government has long resisted allowing its use because of politics and trade concerns that many contend are unscientific.”
https://www.vox.com/future-perfect/24155545/bird-flu-vaccines-h5n1-avian-flu-cows
“Effective bird flu vaccines for poultry have existed for years and are even used routinely in other countries. But, in stark contrast to the Covid-19 pandemic when new vaccines were rapidly developed and rolled out, the US has yet to adopt vaccination as a disease control strategy for bird flu.”