SACRAMENTO  (AP) — Parents who don’t have their children vaccinated will have to get a note from the doctor’s office before enrolling their children in school under a bill that Gov. Jerry Brown announced Sunday he has signed into law.

AB2109 will require parents who enroll students who have not received the required public school vaccines to get a waiver from a physician or a nurse practitioner saying they have received information about the benefits and risks of immunization.

“As a pediatrician, I have personally witnessed children suffering life-long injury and death from vaccine-preventable infection,” Assemblyman Richard Pan, D-Sacramento, said in a statement. He said preventable diseases can spread not only to those who choose not to be vaccinated, but to those who can’t be immunized including infants, cancer patients receiving chemotherapy, those infected with the AIDS virus, or those who are allergic to vaccines.

He noted that Brown signed his bill amid the largest national whooping cough epidemic in 50 years, though the new requirement won’t go into effect until Jan. 1, 2014.

Brown said in a signing statement that the law still allows parents to decide against having their children vaccinated, while ensuring that they make informed decisions about both the risks and benefits.

He directed the state Department of Public Health to oversee the policy to make sure it doesn’t overburden parents. He also directed the department to allow for a separate religious exemption on the waiver form, so that people whose religious beliefs prohibit immunizations won’t have to get a medical professional’s signature.

California Medical Association President James Hay called the bill “a huge step in the right direction for public health.”

Opponents, including former “Saturday Night Live” actor Rob Schneider of Pacifica, said it infringes on parental rights and increases medical costs for families.

“There shouldn’t be government coercion to force parents to jump another hoop to have to make decisions on ... what’s the best interest of their child,” Schneider told The Sacramento Bee earlier this month.