Lawmakers in California moved closer to tightening exemptions for vaccinations, following last month's measles outbreak and the ensuing outcry over the issue across the country.
The state's general assembly approved a bill that would require all children to be immunized before entering kindergarten unless they had a medical condition preventing vaccination.
The law must return to the state senate, which had already approved another draft of the bill, before being sent to Governor Jerry Brown for ratification.
The measure garnered support from both Republicans and Democrats after a measles outbreak in December in the Disneyland theme park affected some 130 people.
In total during the outbreak, 159 cases of were recorded between January and April in 18 states and the country's capital. The viral disease was supposed to have disappeared years ago in the US thanks to vaccination programs.
But when some parents stopped vaccinating their children due to a range of beliefs, measles made a comeback.
The disease is highly contagious. It causes fever and rash and can lead to brain damage, loss of hearing or sight and sometimes death.
Infants, the elderly and those with weakened immune systems are particularly vulnerable.