Why can’t we vax the chickens against bird flu?

There’s the whole egg prices thing going on, and the general reporting consensus seems to claim bird flu is responsible for large scale chicken culls and the culls are responsible for the egg shortage.

So why can’t we vaccinate the birds? The requirements for testing are far lower if you’re vaccinating chickens compared to people, so it won’t take as long to develop one as it did for Covid. They could come out with one and launch immediately and we could stop this dead in its tracks.

For that matter, why can’t we vaccinate the birds against salmonella and prevent food poisoning at its source?