The majority of drivers who get into car crashes have their drivers license.

Since such a vast majority of people have gotten MMR vaccines, this is exactly what we expect right? The vaccine is still doing it's job in vastly reducing spread and reducing severity when people do get mumps.

It could also mean it's outevolving the current vaccine.

Exactly. But the current CDC knows that most people will take away the most simplistic and specious conclusion.

To be fair, this article is from 2021.

That would shift the context to the intent of the recirculation rather than the release. The research is legit, in a vaccum, it's context that's been nurtured in online discourse that creates noise and chaos.