Has any virus actually been headed off with a vaccine already having been created in anticipation of the virus coming into existence eventually? That's really interesting

Edit: and how useful would it be if it was? I was under the impression that covid vaccines were made extremely quickly and that it was regulatory issues that held it until now

In the past, I think the research has been of limited use. However, speculating into the future, with the advances in vaccine development we could possibly see fruit from that sort of research. A lot of the bans on Gain of Function research has recently ended. Still, scary stuff!