If using the law to corral antivaxxers doesn’t work at first, try, try again. At least, that seems to be the lesson learned by New York City Mayor Bill de Blasio. On Tuesday, he declared a state of emergency and mandated residents of the Williamsburg neighborhood, where an outbreak of measles has been raging since last fall, get vaccinated for the viral disease. Those who choose not to will risk the penalty of a $1,000 fine.

New York City’s order, officially issued by the city’s health commissioner, Oxiris Barbot, takes a different tack than the public ban in Rockland. It will require every unvaccinated person who lives or works within Williamsburg, an area of Brooklyn spread across four zip codes, to get vaccinated for measles through the combination measles, mumps, rubella (MMR) vaccine within the next 48 hours (unless they have proof of already having had the disease or are medically exempt). Parents of unvaccinated children will be held responsible for getting them the shot. The order is set to remain in place until at least April 17, when the next New York City Board of Health meeting is scheduled to be held, though they might decide to extend it further.

“This is the epicenter of a measles outbreak that is very, very troubling and must be dealt with immediately,” the mayor said at a press conference in Williamsburg announcing the order. At last count, there have been 285 diagnosed cases of measles in Brooklyn and Queens, primarily among the Orthodox Jewish community.

Though the order applies to anyone living in Williamsburg, health officials will (for now) only reach out to people who might have come into contact with infected individuals and confirm their vaccination history. Those found unvaccinated will then be told to get the shot. Rockland’s ban came with the potential threat of six months jail time and/or a $500 fine, since it would be considered a misdemeanor. Under New York City law, violating this order would instead incur a maximum $1,000 fine.

Both outbreaks in the state are thought to have originated from Israel (the disease was declared eradicated in the U.S. in 2000). It’s not the first time a recent measles outbreak has circulated almost entirely among the Orthodox Jewish community in New York. While the religion as a whole does not shun vaccination, certain rabbis do discourage the practice, often having been influenced by anti-vaccination propaganda.

At the conference, Health Commissioner Barbot said they had received reports of measles parties, events where parents intentionally expose their healthy children to a measles-infected person. But the evidence that these parties have ever really existed is shaky and anecdotal at best. On the other hand, Kentucky Governor Matt Bevin did recently claim that he exposed all nine of his children to a chickenpox-infected person. Chickenpox is another preventable disease that’s starting to bubble back up through outbreaks in the U.S.

What we do know for sure is that while the fast-spreading measles usually causes a mild flu-like illness and distinctive rash, it can sometimes lead to serious neurological problems and even death. These risks are especially heightened among vulnerable populations like the very young who haven’t received their first MMR shot. Typically, the first of two doses is given at 12 to 15 months of age, though Rockland county officials have recommended that kids as young as six months get vaccinated in affected areas.

According to the Centers for Disease Control and Prevention, there are no less than seven ongoing outbreaks of measles, spread across five states, in the U.S. right now. And the current tally of cases (465 and climbing) is already the second largest number of cases reported in a year since the disease was formally wiped out in 2000.