Today I got a flu shot. In my past life, I used to consider people who got such unnecessary vaccinations as "weak," but now I just figure, why not? Who wants to deal with a bad case of the flu, miss work, and possibly end up in the hospital (as I did this summer with a severe case of the stomach flu)? Of course the vaccine doesn't catch all strains of the flu, but hopefully it will at least give me some protection, which is certainly worth suffering through one day with a sore arm.
As I was signing my life away while waiting for the shot (no, I won't sue the school if I have an adverse reaction to the ingredients of the vaccine), the information packet warned that this shot contains thiomersal and that people with known allergies to this preservative should not be getting the shot. We have all heard about the controversy assocaited with vaccines; one side believes that some vaccines might cause autism and other disorders associated with brain development, while the other side does not believe this to be the case. Thiomersal is at the center of this debate.
Looking at its structure, it is easy to see why this compound might be considered suspicious. While it is a powerful preservative because of its antifungal and antiseptic properties, it also is an ORGANOMERCURY compound. Basically one of the reagents that I wouldn't like to work with in lab. You only have to read the story of Prof. Karen Wetterhahn (which was posted for some time in our group's hallway as one of those 'be more careful in lab' warnings) to know why I might refuse to work with alkyl mercury compounds. Basically the harmless sounding name thiomersal actually refers to a compound that probably breaks down to ethyl mercury inside of your body. At the same time, it is a necessary part of the vaccine and works to prevent possible adverse side effects like as bacterial infection that might occur in vaccines lacking preservatives. And is ethyl mercury just as bad as methyl mercury? Apparently not , but that doesn't stop parents from worrying about their children.
Personally, I wouldn't be too worried about thiomersal containing vaccines. In general, very few vaccines contain thiomersal any more, and those that do have extremely low levels present. Looking at this table, some vaccines contain 0.01% thiomersal. In studies, levels of thiomersal producing inorganic mercury levels ranging from 201 micrograms/Liter to 50 milligrams/L were shown to be toxic in cell culture, (and, for those interested, these levels induced activation of caspase-3). Levels of thiomersal used under normal vaccination conditions are much much lower. In the worst case scenario, after a complete series of vaccinations a very very small child would receive less than 50 micrograms of inorganic mercury per kg of body weight. Additionally, ethyl mercury (half life of about 18 days in the bloodstream) does not bioaccumulate like methyl mercury (half life of 50 days).
So go ahead and vaccinate your children. And why not get a nice flu shot for yourself while you are at it?
 How do I know ethyl mercury isn't near as toxic as methyl mercruy? Of course there have been some scientific studies completed on this very subject, but I also have some firsthand experience. Thiomersal was once sold as Merthiolate. I am not that old yet, but I still can remember back to when my dad would put this bright pink solution on any little cuts or scrapes that I would have. It always stung for a second, but nothing ever got infected. Strange to think that it was actually an ethyl mercury containing product. In 1998 the FDA banned the use of thiomersal in over the counter products, which explains why I haven't been able to find this wonder drug from my childhood in any stores.