All vaccines contain risk factors, some life threatening and debilitating. It’s in the listed side effects. I’ve never seen a single case of any of those listed side effects in my life. But, in my employment you would be hard pressed to find a set of parents related to the service users I serve that didn’t note an overnight change in their child post-MMR into autism. I had the same experience with one of my own children, but not the other. Literal overnight change. Full body rash accompanied by instant developmental and social regression. And research isn’t weighed on how many things say yes and how many say no unless there is a good reason to doubt the limited counter. If the research is conducted appropriately, both are as viable as one another, particularly when they are based on cross sections of societies. Example: For years studies were published about smoking. Everyone knew it gave you cancer but study after study came out saying that they found no link. Tobacco companies were suing people and countries for saying they caused cancer, and they were winning. No exact biological mechanism was found. Smoking didn’t start causing cancer when the research tipped the other way, or when the biological mechanism was found. Only thing that changed was ignorant sheep started paying attention.