The major issue with mercury is that it is bioaccumulative, also called biomagnification. It does not stay in the blood for long and will settle in what appears to be the genetically weak parts of an organism. For some that's the pancreas(diabetes), for others it can be the brain(CFS, Parkinsons, Alzheimers, autism), nerve cell endings(multiple sclerosis), and the bowels(Crohn's disease, IBS).
The health industry is now saying mercury poisoning comes from fish. So let's say this is mostly true. What happens when the person gets a huge dose of mercury from a flu shot when they are already toxic? The health industry now recommends flu shots for people every year! Eli Lilly is lobbying to have everyone get their shots. Why would they do that?
The trillion-dollar-pharmaceutical industry lobbies governments for laws requiring vaccinations. Claiming a need for safety, their corporations add preservatives like mercury-laden Thimerosal. These same companies then sell drugs that only treat the symptoms of mercury poisoning, claiming they know not the underlying cause of diseases, as the now suffering-vaccine recipients become lifelong customers.