So, obviously, autism - which is the key in this - is a very big problem. We need more studies about it. We certainly have to try to figure out what causes it and why and do something about it. But to tab it to vaccines, I think, is a real mistake. Not only is there no evidence, but what it leads to is larger numbers of unvaccinated children. And that's not only a problem for polio. It's a problem for a wide range of vaccine-preventable diseases.