A bill eliminating vaccine exemptions for personal and religious reasons was signed into law by Gov. Jerry Brown on Tuesday, the Associated Press reported.
California has become the third state in the country, along with Mississippi and West Virginia, to impose such a strict school vaccination law.
In a statement, Brown said the "science is clear that vaccines dramatically protect children against a number of infectious and dangerous diseases."
The bill, which would also require parents to cite a medical reason for not vaccinating their children, was approved by the state Assembly last week with some amendments, which the Senate approved on Monday, the Los Angeles Times reported.
Brown hasn't said if he plans to sign the bill, but a spokesman told the Associated Press last week that the governor believes vaccinations "are profoundly important and a major public health benefit, and any bill that reaches his desk will be closely considered."
If the bill does become law, California will have one of the strictest vaccination regulations for school kids in the U.S.
The bill was proposed in February after a series of outbreaks of diseases vaccines are designed to prevent. The most high profile of those outbreaks began in January, when multiple people were exposed to measles at Disneyland.
The bill, however, has been hotly contested among parents, with those who want the option of not vaccinating their children staging rallies and lobbying lawmakers to kill the legislation.
According to the AP, Renate Krogdahl, a mother of three, told demonstrators last week that parents like her "are being bullied into having their children vaccinated, or not sending their kids to school."
On the other side of the debate is Carl Krawitt, whose son Rhett has been fighting leukemia for 4 1/2 years and so couldn't be vaccinated. Krawitt told BuzzFeed News Thursday that when the measles outbreak began spreading in California, he asked his school district in Marin County to prohibiting unvaccinated children from attending so that Rhett's sister wouldn't get sick.
"It she were to get sick and bring one of these diseases home, it could impact our son’s chemotherapy and be lethal," Krawitt said. "People don’t truly understand the risk if these diseases actually have an outbreak."
Over last few months, the family's story has received extensive media coverage, and the family publicly supported the proposed legislation. On Wednesday, they personally delivered a petition with thousands of signatures in support of the bill to the governor's office.
Carl compared the bill to past legislation requiring seat belts or prohibiting smoking in public places.
"There are personal freedoms," he added, "and there are limitations where those personal freedoms impact others."