New York City officials declared a public health emergency Tuesday in parts of the Williamsburg neighborhood, where a measles outbreak has run rampant in an Orthodox Jewish community since last October-largely among unvaccinated children.

The announcement comes a day after DOH threatened to close Williamsburg yeshivas that allow unvaccinated students to attend school in light of the epidemic.

Added de Blasio: "We can not allow this unsafe disease to make a comeback here in New York City".

Mayor Bill de Blasio announced the unusual order amid what he said was a measles crisis in Brooklyn's Williamsburg section, where more than 250 people have gotten measles since September. Barbot said that 21 people have been hospitalized, and five have ended up in the intensive care unit. "Those who have not received the MMR vaccine or do not have evidence of immunity may be given a violation and could be fined $1,000", Mayor De Blasio's office said in a statement.

The health order applies to anyone living, working or going to school in four zip-codes in the neighborhood and requires all unvaccinated people at risk of exposure to the virus to get the jab, including children over six months old.

In the modern era, measles is rarely fatal, but Center for Disease Control numbers showed 1 in 10,000 cases resulted in death before 1963.

"To challenge the unsafe misinformation that is being spread by a group of anti-vaxxers, it's crucial that everyone around them be vaccinated to shield them from infection", Barbot said.

Officials fear increased travel during Passover among people who could carry measles to or from NY. But over time, school-vaccination requirements - which the high court upheld in 1922 - became the centerpiece of public health officials' strategies to fight measles, mumps and other communicable diseases.

"There is a campaign with very intentional efforts to give misinformation", Herminia Palacio, the city's deputy mayor for public health, said at the news conference.

Israel, for instance, also has a current measles outbreak.

"It's true that a lot of people have measles and measles are not a very good thing, but I think the vaccine also not a very good thing", said Aron Braver, a neighbourhood resident.

Tuesday's announcement was the first time NY has ordered mandatory vaccinations in recent history, according to health officials. "All rabbis, all prominent rabbis have issued proclamations that everyone should vaccinate". "Unvaccinated people continue to get measles while overseas and bring the disease into the United States and spread it to others". It says the vaccine is 97% effective.

A recently released large-scale Danish study looked at any possible risk for autism from the MMR vaccine and the conclusion was that "MMR vaccination does not increase the risk for autism, does not trigger autism in susceptible children, and is not associated with clustering of autism cases after vaccination".

The best protection from measles is to have two MMR vaccinations.