Further Reading Personal vaccine exemptions under fire in California—and by AMA

On Tuesday, California Governor Jerry Brown (D) signed into law one of the most stringent vaccination laws in the United States, eliminating the state's previous personal and religious belief exemption for vaccines.

Under the new law, which takes effect January 1, 2016, all California schoolchildren must prove that they have been vaccinated in order to attend school. They can only be exempted when that child’s physician explicitly approves it.

"The science is clear that vaccines dramatically protect children against a number of infectious and dangerous diseases," Brown wrote in a signing statement. "While it’s true that no medical intervention is without risk, the evidence shows that immunization powerfully benefits and protects the community."

Children who are homeschooled do not have to be vaccinated.

In April 2015, when the bill passed a senate committee, one of the bill’s authors, himself a pediatrician, lauded the move.

"Vaccines are one of our greatest medical advancements, and to protect the health of our students and our greater community, this bill is urgently needed to boost vaccination rates," Dr. Richard Pan, a state senator representing Sacramento, said in a statement. "This measure will ensure that students whose parents choose to not vaccinate them have several educational options that don’t put other children at risk of contracting vaccine-preventable diseases."