 Are over half of Americans hesitant to vaccinate their dogs? Here's what they say. Wait, dog autism? Vaccines don't cause autism. Also, dogs can't even have autism. Dog vaccines are needed to stop the spread of diseases like rabies amongst humans, which experts are worried might start rising. And you don't want rabies. It's nearly 100% fatal once symptoms appear. Also, you don't want your pup getting parvo or distemper, both of which can be deadly.