Only children with serious health problems may opt out of school-mandated vaccinations under the new law signed Tuesday by California's governor.
Democratic Gov. Jerry Brown explained his decision to sign the bill that has prompted fierce debate by writing, "evidence shows that immunization powerfully benefits and protects the community."
The law removes California's personal belief exemption for immunizations, requiring nearly all public schoolchildren to be vaccinated.
"This is truly a case where science -- and what is the best case for public health -- prevailed," said Senate President Pro Tem Kevin de Leon, D-Los Angeles, at a press conference Tuesday.
California's proposal is intended to boost vaccination rates after a measles outbreak at Disneyland last year.
It has prompted the most heated legislative debate of the year with thousands of opponents taking to social media and protesting legislative hearings.
Kimberly McCauley, a Sacramento resident with a 23-month-old daughter, was among a small group of parents holding vigil at the Capitol when they learned of Brown's signing Tuesday morning.
McCauley's eyes filled with tears.
"She will go to school. And then, when she is denied at kindergarten, I will sue," she said.
While medical exemptions would still be granted to children with serious health issues, other unvaccinated children would need to be homeschooled.
Rebecca Estepp of Poway told NBC 7 she was “so sad” to learn the governor signed the bill into law.
Her 17-year-old son, Eric, was vaccinated when he was young. His mother says vaccines caused his brain to swell and then he developed autism.
“Most families are like mine,” Estepp said. “We didn't know we had a problem, a genetic susceptibility to vaccine injury, until it was too late. So this law is going to put families like mine with genetic susceptibility at risk for more children to be harmed just like my son was."
However, Marissa Cortes-Torres of Carlsbad said she was relieved to know the governor was thinking of the health of children.
Her son, Ramon, died when he was 9 years old from complications of measles.
“For the mother who believes her child or other parents who believe that the vaccines cause autism, I would rather have a child with autism and know that I can kiss them and hug them and put them to bed at night than to know my child is no longer alive,” Cortes-Torres said.
She believes the law was long overdue.
California joins Mississippi and West Virginia as the only states with such strict requirements.