I have mixed feelings about this article linked at the end of this post. On the one hand, it's great, because it has the potential to produce a great product. On the other hand, the implication seems to be that they're infecting chickens with a live COVID virus (they use the word 'infect', rather than immunize, which is why I infer that). The problem with this is that if the virus is live, it could adapt within chickens to spread easily to other chickens (especially if this is done a lot), and then breed new forms of COVID-19 (which may or may not spread back to humans, and which might affect the chicken/fowl industries), making the pandemic worse.
The solution would seem to be to develop a non-live COVID-19 vaccine for chickens, innoculate the chickens, and then use their eggs. They might as well vaccinate the chickens for everything else while they're at it.
Even if all the chickens are isolated and infected at the same time, I'm still uneasy about that, considering COVID-19 can linger in the gut for a long time after recovery, if what I've heard is correct.
Plus, with a live virus, isn't there a risk of infecting humans with the eggs? Birds don't usually have COVID-19, so I don't know that anyone has studied this.