Corus - re "the best choice for the individual is to be one of a small number of freeloaders. Unfortunately this increases risk for everyone. So how do you suggest it's dealt with?"
If you want to increase the number of people who vaccinate, you need to lower the perceived risk of the vaccine.
They tried doing this by crucifying discrediting Wakefield and saying over and over that MMR isn't risky. Well, that didn't work very well.
The way they haven't tried is to address people's fears and legitimate concerns (like not wanting to vaccinate against rubella) and offer single vaccines.
"Appeal to people's better nature? Not going to work."
Not only "not going to work", but ethically indefensible. You can't ask people to do something that is not in the best interests of their baby and has a small risk, for the benefit of some stranger adult.
"Make vaccines compulsory? That's going to be very unpopular."
Compulsory vaccination happens when the disease is truly terrible and the vaccination is clearly in the interest of the child. It is not ethical when the disease is a very mild childhood disease and it can't happen.
"I think social pressure has the best chance - those of us who vaccinate expressing how selfish we think the freeloaders are"
Good luck with that. I couldn't care less if you call me a 'freeloader', especially since I actually want DD to have rubella and be immune for life.
I think you will find that most parents will be thinking "Take an unnecessary risk on the well-being of my baby or be called a 'freeloader'. Ooooh, what a tough choice. Not." 