We have a huge issue with ticks here, and have had problems with abortion due to tick borne fever 3 years ago. We now use Dysect, but be careful with it, it is really nasty stuff - my OH can't use it at all, and I can do about 100 sheep then need a break from the smell. It also corrodes the tubing from the bottle to the gun, which tells you quite abit about how horrid it is. It is by far the most effective thing against the nasty little monsters though.
I don't know anything about vaccinating as we don't really tend to buy sheep in, but if we do, they are kept off the hill.
Trying to get rid of them is pretty much impossible, I would have thought, although we are looking at options to try to reduce our bracken - helicopter would be most effective but very expensive, or possibly a trailed weed wiper for behind the quad, although there would then be considerable areas where it wasn't safe to go.