What you say is true, however, if all those at high risk get their vaccines, it doesn't matter about the spread. Getting it isn't the problem. Most recover just fine. It's those at high risk that are the problem, or those that when things progress to the point they do need medical intervention, don't go get it. That's when it becomes dangerous. The vaccine can help with that.The flu vaccine it the same and will let you not get sick but still spread the virus as is polio