Here are two facts that one clearly admit and and almost read everywhere:
Fact 1) it needs many years to elaborate a vaccine (from research, creation, testing and approval)
Fact 2) new vaccine for flu influenza are elaborated twice a year...
I am sure that you understand that is non consistent. So i certainly am missing something here...
-does it mean no efficiency test are realized for flu?
-does it mean seasonal flu is actually the same virus? (in that case it would not be advised to do yearly vaccination, right?)
-is this something else i am totally missing out?
Thanks for explanations