The People at Science believe it has to do with not providing enough solid scientific information for sceptical parents. They even report that the major outbreaks in preventable diseases in the USA can be attributed to people that have intentionally not vaccinated. I have a different reason why some viruses are becoming prominent again while vaccines exist for them.
The answer is STUPID PEOPLE!!!!! Anti-vaccination idiots who think irrational things like vaccines give autism. Idiots who think the government is out to inject micro chips into them when they get the flu shot. There is enough verified scientific evidence showing that vaccines are safe, if you do not believe this you are an either an idiot, conspiracy theorist or mindless sheep.
If you are not getting your vaccines YOU ARE AN IDIOT. You are putting others at risk by not getting these vaccines. If that's the way you want to play, bugger off to your island and do not be part of normal society. If you want to be an outcast and not have access to modern day hospitals, junk food, department stores etc. then don't get your vaccines but also get the hell out of my town.