According to a recent study conducted by the CDC, there is no no clear link between early exposure to the preservative thimerosal (a preservative used in some vaccines) and problems with brain function and behavior in children age 7 to 10.
On our local playground, parent discussions of the vaccinate/don't vaccinate variety can come nearly to blows - it is a contentious parenting issue.
According to this article, there may be good news for families who avoid vaccinating their children due to concerns that thimerosal exposure in the vaccine may cause neurological issues. In a study of 1,047 children exposed to thimerosal via vaccination, researchers could find not consistent pattern of exposure and neurological problems.
Up next in this research is a study specifically aimed at researching thimerosal exposure and autism, and the results of that study are due out next year. Do you vaccinate your kids? Why, or why not?