All shots in the US are allowed to contain a mercury based preservative called thimerosal. This chemical is banned in the EU.
Some shots come a in "preservative free" variety at your request. Not all shots are available this way. If you are concerned about mercury in your vaccines, request the preservative free kind or don't get them.
The seasonal flu vac usually contains thimerosal. The thimerosal free version is often available but must be ordered. More thimerosal is needed in combo vacs to keep the different strains from interacting with one another.
at 8:55 PM on Nov. 15, 2009