California on Tuesday became the largest state in the country to require schoolchildren to receive vaccinations unless there are medical reasons not to do so, as Gov. Jerry Brown signed legislation that ended exemptions for personal or religious reasons.
Mr. Brown, a Democrat, signed the bill after it was passed by significant margins in the State Legislature. The new law was the subject of a long and heated debate in reaction to a strong movement among some parents who refuse to vaccinate their children against infectious diseases like measles.
“The science is clear that vaccines dramatically protect children against a number of infectious and
dangerous diseases,” Mr. Brown said in a statement. “While it is true that no medical intervention is without risk, the evidence shows that immunization powerfully benefits and protects the community.”
Two other states, West Virginia and Mississippi, have similar vaccination requirements. Despite overwhelming evidence that vaccines are an essential public health measure, the number of unvaccinated children in California has been rising, partly because personal and religious exemptions have been easy to obtain.
Doctors say that parents who decline vaccines for their children, taking heart from the fact that most other children are immunized and unlikely to spread diseases like measles, have helped create pockets of dangerously low immunity levels in particular schools and communities.
An outbreak of measles in California this year, which began at Disneyland, was attributed in part to the disease’s being spread by children who had not been vaccinated.
Under the new law, families with a nonmedical reason for declining vaccines will have to home-school their children. Unvaccinated children who are currently in school will be allowed to remain, although they will be expected to show proof of vaccination when they enter kindergarten and seventh grade.