Jim Carrey takes part in a rally

Actors Jenny McCarthy (L) and Jim Carrey, carrying her son Evan, take part in a rally calling to eliminate toxins from children's vaccines near the Washington Monument June 4, 2008. Various U.S. government agencies and non-government health experts agree there is no evidence that can link autism to any kind of vaccine, but a small and highly vocal group of activists remain unconvinced. [Agencies]