A first-of-its-kind order in America barring children who have not been vaccinated for measles from public places took effect on Wednesday in Rockland county, north of New York City.

The emergency order came as concern grows in jurisdictions around the US about outbreaks of the disease, which has surged back as parents refuse to get their children vaccinated.

Rockland county has seen 153 confirmed cases of measles since October – and only 73% of children under 18 in the area are fully vaccinated, officials said.

“We must not allow this outbreak to continue indefinitely or worsen,” said county executive Ed Day. “We will not sit idly by while children in our community are at risk.”

The emergency order, which took effect at midnight, says that children who have not been vaccinated must stay away from schools, shopping centers, restaurants, houses of worship and all other indoor public places. Outdoor locations like parks and sidewalks are not covered.

As of early Wednesday, no one had been cited for violating the order, said county spokesman John Lyon. Parents who violate it could face up to six months in jail or a $500 fine, but law enforcement will not be actively asking citizens to show their vaccination records.

The county has vaccinated nearly 17,000 people since the outbreak began in October, but resorted to the sweeping order targeting unvaccinated kids after other measures failed to rein it in.

“Our inspectors have begun to meet increasing resistance from those they are trying to protect,” Day said. “Our health inspectors have been hung up on, or told not to call again. 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. This type of response is unacceptable and frankly irresponsible. It endangers the health and well being of others.”

The county is bracing for a likely legal challenge to the order. A group of parents sued over an earlier order barring unvaccinated children from schools, and may challenge the new declaration as well.

Measles began to spread in October in both Rockland county and New York City, where there have been 214 cases of the disease. The outbreak has been concentrated in the Orthodox Jewish community, where vaccination rates tend to be lower. It began with residents who got measles while traveling in Israel, which is battling a major outbreak, public health officials say.

In New York City, the health department threatened five yeshivas with fines for allowing unvaccinated children – including some infected with measles – to attend school in violation of previous orders. The schools are now in compliance, the department said Wednesday.

Top rabbis and other community leaders have urged residents to get vaccinated, and most children in the community do get the shot.

But anti-vaccine groups have spread misinformation in the community, including through a parent handbook and telephone hotline. Messages from authorities and mainstream news sources don’t always make it to residents of tight-knit Orthodox neighborhoods.

“This community was deliberately targeted by anti-vaccine activists,” said Dr Peter Hotez, the dean of the national school of tropical medicine at Baylor College of Medicine.

Other measles outbreaks have happened this year in Washington, Texas, California, and Illinois. Public health officials are likely keeping a close eye on Rockland County’s latest order to see how well it works.

“If it seems to be helpful, I wouldn’t be terribly surprised if other states in the midst of a measles outbreak would consider it,” said Daniel Salmon, a professor at the Johns Hopkins Bloomberg School of Public Health.

Outbreaks typically start with children whose families have refused vaccinations, and may spread to children who are too young to get the vaccine, can’t get it for medical reasons, or in rare cases where the vaccine fails.

“There’s good evidence to suggest that what they’re doing will make a difference,” Salmon said.

At the Palisades Center Mall in West Nyack on Wednesday, one of the locations where officials say shoppers may have been exposed to measles, several parents said they support the order.

“My priority is her safety,” said Sulier Hilario, 34, who was shopping at Best Buy with his five-year-old daughter, Grace. “I just don’t understand why people aren’t [getting the vaccine] … Whatever parents want to do with their kids, that’s their problem, until it affects mine.”

Eric Shuda, 33, agreed. His 15-month-old daughter is vaccinated, but he worried for babies too young to get the vaccine. “I think it’s smart,” he said. “God forbid, if my daughter was supposed to get her measles vaccination next month ... and we go into the mall, and someone has that. Then she has that chance of getting exposed.”