There are a number of reasons why anti-vaccination hysteria has grown in the US. Underlying them all is a modern irony: the success of vaccines in the developed world has allowed Americans to easily ignore the fact that right up until a scant few decades ago, infectious disease was hands down the number one killer of humanity:
One wonders what public tortures Jonas Salk might have encountered had he presented his polio vaccine today rather than in the 1950s. One crucial difference is that polio left visual reminders of its assault on the human body. The 1952 epidemic affected nearly 58,000 people, more than 3,100 of whom died and some 21,000 were left disabled. Most Americans under the age of 50, including doctors, have never seen measles.
Meanwhile, the anti-vaccination industry marches on, eager to capitalize on the latest news. Because anti-vaxxing isn't just a conspiracy claim, it's a business. Expecting those businesses to close up shop in the face of facts is as realistic as thinking an advertising firm paid to market soft-drinks will suddenly announce that vegetable juice is healthier.