Rockland County, New York, has declared a state of emergency following a severe outbreak of measles.
The county, on the Hudson River north of NYC, has barred unvaccinated children from public spaces after 153 cases were confirmed.
Violating the order will be punishable by a fine of $500 and up to six months in prison.
The announcement follows other outbreaks of the disease in California, Texas, Washington, and Illinois.
Vaccination rates have dropped steadily all over the country with many parents objecting for philosophical or religious reasons, or because they believe discredited information that vaccines cause autism in children.
Rockland County Executive Ed Day said: “We will not sit idly by while children in our community are at risk.
“This is a public health crisis and it is time to sound the alarm.”
According to the New York Times, the outbreak in Rockland County is largely concentrate in the ultra-Orthodox Jewish community. It is believed it could have spread from other predominantly ultra-Orthodox areas around New York which have already seen outbreaks of measles.
Ed Day said health inspectors had encountered “resistance” from some local residents, which he branded “unacceptable and irresponsible”.
“They’ve been told <<We’re not discussing this, do not come back>> when visiting the homes of infected individuals as part of their investigations,” he said.
According to the CDC, there are 314 cases of measles currently reported in the US, with nearly half of those coming from Rockland County. The authorities had been making steady progress in encouraging religious communities to immunize children but communication had broken down in the last month.