Since most of the U.S. trading partners would not accept vaccinated chickens to begin with:

 It is unlikely that most U.S. Egg producers would want to vaccinate their chickens IF they ship chickens to other countries to begin with. However, it is possible that people selling chickens in the U.S. might consider vaccinating their chickens for H5N1 Flu Virus. So, it's debatable who will vaccinate and who won't unless the government requires this of all chicken growers in the U.S. Also, States might have different things to say about al this too.