Hillary Clinton says 'the science is clear' on vaccinations for children

Hillary Rodham Clinton is tweaking Republicans who say vaccinations should be optional, writing on social media that vaccines protect the lives of children.

Clinton says on Twitter, "The science is clear: The earth is round, the sky is blue, and (hashtag)vaccineswork. Let's protect all our kids." The potential Democratic presidential candidate ends her Twitter commentary with the hashtag GrandmothersKnowBest.

Clinton's tweet on Monday night came after New Jersey Gov. Chris Christie said parents should have choice in the matter. His office later clarified his comments, saying that with a disease like measles there's no question kids should be vaccinated. Christie is a potential Republican presidential candidate in 2016.

House Speaker John Boehner and House Democratic leader Nancy Pelosi say separately that children should be vaccinated.