There are already a few vaccines which can be made to work, and some others already being made.

So far the cases in Cambodia do not look as though they are spreading from person to person, but who knows, the news is so new that only time will tell. These events have happened in the past, and all of the infected people were working with birds, or living at the homes of people who do, which is so far the only way these rare events happen. If it does start to spread among humans, from person to person, it will be easier to contain as flu viruses are not nearly as contagious as Sars Cov 2. Flu is not really air borne, its droplet spread. There are also quite a few vaccines already made and ready for use.