When California recently (June 2015) passed a law banning the personal belief exemption of routine childhood vaccines Jim Carrey recently posted (June/July 2015) a series of tweets about thimerosal (a form of mercury) used as a preservative in vaccines. Is it true that there is no convincing scientific evidence that thimerosal causes harm by the low doses of thimerosal in vaccines, except for minor reactions like redness and swelling at the injection site?

Yes, there is no convincing scientific evidence that thimerosal causes harm by the low doses of thimerosal in vaccines, except for minor reactions like redness and swelling at the injection site

Explanation:

Thimerosal has been used safely as a vaccine additive, added to some vaccines to prevent germs like bacteria and fungi from growing in them dated since early 1930s. Though, Thimerosal contains mercury but the type of mercury doesn’t stays in the body, and is unlikely to make human fall sick.

Most people doesn't have any allergic reaction to it except for redness and swelling at the injection site as early mentioned and this is considered irrelevant when compared to effect of vaccine when contaminated by germ which could cause serious illness or death.