On Tuesday, California Gov. Jerry Brown signed into law a bill that requires mandatory vaccinations for almost every school child in the state. The law strikes the state’s previous exemptions for personal or religious beliefs. Children with medical problems, including immune-system deficiencies, will be exempt. Parents who decline vaccinations will have to enroll their children in home-based private schools or off-campus public independent-study programs. “The science remains unequivocal that vaccines are safe and vaccines save lives,” said state Sen. Richard Pan, who co-authored the bill.