After Chris Christie's call for "choice" in vaccination landed him in trouble, Hillary Clinton is making no bones about her own position. "The science is clear: The earth is round, the sky is blue, and #vaccineswork. Let's protect all our kids. #GrandmothersKnowBest," she posted on Twitter last night. Her comments also come after a third potential 2016 candidate, Rand Paul, suggested that vaccines be "voluntary," USA Today reports. While Clinton's views seem clear, some commenters point to a Washington Free Beacon report noting that in 2008, neither she nor Barack Obama seemed so sure about vaccines. (More Hillary Clinton stories.)