It has nothing to do with a maze. He is referring to the ship of Theseus. Which over time had planks and oars replaced such that at some point, the question was posed as to whether this was still the same ship of Theseus. The vaccine changed many times, so he is saying it is difficult to know what is what. That's what I think is meant anyway.

I was quoting lyrics to a song called Maze, btw. Phish