Former Secretary of State Hillary Rodham Clinton is widely expected to announce a presidential campaign in the coming months, but has maintained a low profile since mid-December. (AP Photo/Carolyn Kaster)

Hillary Clinton weighed in on the growing debate over mandatory vaccination late Monday night, writing a forceful statement of support over twitter.

The former secretary of state, who is widely expected to launch a presidential bid for the Democratic nomination later this year, made a passing reference to her newborn granddaughter Charlotte in the tweet.

Mandatory vaccination has emerged as a potent political issue among potential 2016 contendors. On Monday, New Jersey Gov. Chris Christie, who has been making moves to launch a bid for the GOP nomination, was forced to walk back a call for "balance" on vaccination after critics called his remarks irresponsible. Kentucky Sen. Rand Paul, and doctor and also a Republican presidential contender, on Monday afternoon told radio host Laura Ingraham that he believes most vaccines should be voluntary.

The candidates' comments come after President Obama weighed in Sunday, saying "there is every reason to get vaccinated — there aren’t reasons to not."

The CDC is urging people to get vaccinated for measles amid an outbreak that began at Disneyland and has now spread to other states, including Utah, Washington, Oregon and Colorado. (Reuters)