[clarents]

Wow, you're right, I guess that kind of kills my theory. I knew that flu was which explained why there's a new vaccine every year and it's often not effective against the current strain. But I had thought that polio and measles were DNA viruses.

[Fomite]

You are partially right. Some RNA viruses are hard to vaccinate against because of their mutation rate, but it's not the sole arbiter of whether or not it's doable.

There are other issues, like the existence (and lack thereof) of highly conserved antigenic targets.