Vinegar can possibly kill the flu virus like it does some other germs and viruses.
However there's no scientific evidence as of now that says for sure whether or not the flu virus can be killed off using vinegar.
Vinegar does have some natural disinfecting properties though as it's acidic and most germs and viruses cannot thrive or live in acidic environments.
So some viruses can be killed up with the use of vinegar.
But to be sure viruses such as the flu virus or the new Covid 19 Virus is killed off you should use regular disinfectant.
It might cost more to buy disinfectant but your health and your families health is worth it.