I appreciate your injection of a scientific approach to our discussions on here, or in this case somewhat of a mathematical approach. As you probably know, you just used the statistical concept known as, "Correlation is not the same as causation". We have to be very cautious about jumping to conclusions just because two things appear to be related. That being said, I am not trying to say right or wrong about the Shingrix vaccine causing Grover's, but I agree that as is the case of so many things related to GD, "We just don't know". Much more scientific research is needed, but I'm not holding my breath waiting for THAT to happen. We appear to be pretty much on our own for now.