Carrey has been a critic of the scientific consensus that no evidence links the childhood MMR vaccination to the development of autism, and wrote an article questioning the merits of vaccination and vaccine research for the Huffington Post. With former partner Jenny McCarthy, Carrey led a "Green Our Vaccines" march in Washington, D.C., to advocate for the removal of toxins from children's vaccines, out of a belief that children had received "too many vaccines, too soon, many of which are toxic"