As it does in humans.
It’s known as vaccine escape.
Virologists have known this for decades… I remember them warning about it back when H1N1 was going around. They all agreed that you don’t vaccinate your way out of a pandemic
" A new international study suggests that vaccines may be driving bird flu evolution, as efforts to contain the spread of the virus face increasing challenges.
Amid growing concerns about potential human cases, a new analysis has found increasingly resilient bird flu strains are arising globally.
Despite this, significant concerns for rapidly spreading H5 bird flu infections remain isolated within avian populations."
Mass Poultry Vaccines
"In many countries, farmers feed livestock with steady doses of antibiotics and vaccines to keep them healthy until their turn at the slaughterhouse
or as they continue to produce milk and eggs for animal agriculture.
The highly pathogenic H5 group of avian influenza virus, which includes H5N1, came into focus in the new research.
The team studied H5 viruses in the wild and among poultry farming in agriculture,
with an eye on comparing countries where poultry vaccinations are or are not routine practice.
Currently, H5N6 is the most common variation in China, and its evolution may be vaccine-driven."
….
"When The Debrief asked co-author Oliver Pybus of the Royal Veterinary College University of Oxford whether slowing the spread
or virus evolution was the most pressing concern, he said, “That’s a really interesting question.
In short, they are intimately linked.
Virus evolution only occurs when the virus transmits, so the more opportunities for infection there are, the greater the potential for more virus adaptation.”
"While H5N1 bird flu has led to 67 confirmed cases and even one death in the United States, according to the CDC,
the forbidding virus has yet to become a significant problem for humans.
Pybus said that his work did not raise any immediate concern about the imminent spread of the virus to humans." (Emphasis mine)
“All previous human flu pandemics were caused by H1 or H3 viruses. We still don’t fully understand why H5 has not evolved to transmit among humans,” Pybus commented.
But he did note that to keep poultry populations safe, “It’s clear that we need to enhance our surveillance of people who come into frequent contact with wild birds, poultry, and infected cattle.” (The article continues...)