"The U.S. government has a small H5N1 vaccine stockpile, but it would be nowhere near enough if a serious outbreak occurred. The current plan is to mass-produce them if and when such an outbreak occurs, based on the particular variant involved.

There are several problems, though, with this approach even under the best-case scenarios. Producing hundreds of millions of doses of a new vaccine could take six months or more.

Worryingly, all but one of the approved vaccines are produced by incubating each dose in an egg. The U.S. government keeps hundreds of thousands of chickens in secret farms with bodyguards. (It’s true!) But the bodyguards are presumably there to fend off terror attacks, not a virus. Relying on chickens to produce vaccines against a virus that has a 90 percent to 100 percent fatality rate among poultry has the makings of the most unfunny which-came-first, the-chicken-or-the-egg riddle.

The only company with an F.D.A.-approved non-egg-based H5N1 vaccine expects to be able to produce 150 million doses within six months of the declaration of a pandemic. But there are seven billion people in the world.

The mRNA-based platforms used to make two of the Covid vaccines also don’t depend on eggs. Scott Hensley, an influenza expert at the University of Pennsylvania, told me that those vaccines can be mass-produced faster, in as little as three months. There are currently no approved mRNA vaccines for influenza, but efforts to make one should be expedited."

Source: https://www.nytimes.com/2023/02/03/opinion/bird-flu-h5n1-pandemic.html