It doesn't have to have to mutate cells for there to be long-term affects on the body. There's the possibility of gradual chemical buildup (where chemicals don't leave the body and accumulate in places that disrupt bodily processes). I wholeheartedly support this vaccine from the data, but for those who have a higher chance of dying from allergic reactions or heart problems from the shot (like those under 18 with no underlying health problems), there is reason to believe that there's something happening in relation to the body in some mysterious way (for some teenagers) that there are side affects for those people for some unknown reason (in relation to the vaccine). Since heart problems gradually happen overtime more often than not, I see reason to believe that this can be a long-term affect, though you are probably right that it is insignificant. I'm not trying to offend anyone here, it's just that I understand what's in the article and think that the scientists probably overlooked a few things because it seems insignificant. I'm just a chemistry nerd. Good article, though. :)