Again: Thimerosal is a molecule that has an atom of mercury as a constitutive element. It is therefore not really proper to say that the vaccine "contains mercury". You cannot treat a molecule with an atom of mercury in its structure the same as elemental mercury, which is what the quote you give above is trying to do.
Frankly, I think all the attention that some people pay to the mercury in the flu shot is pretty ridiculous. Healthwise, most people should be worrying about things that are much more pressing, such as the amount of sodium and fat they're getting every single day, instead of the amount of mercury they're getting in their flu shot, which you get only once a year.
Case in point: I ate food that contained both chlorine (a toxic hallogen) and
sodium (a dangerously reactive metal) today.
It tasted salty.