New York City mayor Bill de Blasio has declared a public health emergency in Williamsburg after the area logged 300 measles cases in the past months. The cases, mostly located in Brooklyn, finally prompted the government to require unvaccinated individuals to receive the vaccine immediately, otherwise they would be fined $1,000 for refusing.

In a Twitter post, Mayor de Blasio emphasized that “vaccines are safe and effective—and that they work.”

His decision and comments came after the city has been trying for months to disseminate information through various channels to get people to get vaccinations for themselves and their children. However, many of those who did not believe in vaccines remained steadfast in their refusal.

The Order of the Commissioner issued on the official government website identified zip codes 11205, 11206, 11211 and 11249 as the most active sites of the measles outbreak. The same document said that the city is responsible for controlling the contagious disease and thereby orders parents and guardians of unvaccinated children ages six months and up should bring them in for MMR shots within 48 hours from the date of the order.

Failure to comply, the document warns, is qualified as a violation of the New York City Health Code. This can be subjected to criminal and civil fines, forfeitures, penalties, and even imprisonment.

At the news conference for the order, City Health Commissioner Dr. Oxiris Barbot said that the point of the firm directive is not to fine or penalize residents, but to make it easier for people to access the measles vaccine. Those who still refuse despite facing fines will be dealt with on a case-to-case basis after consultation with the city’s legal team.

MMR vaccine
This picture taken on April 5, 2019 shows a nurse preparing the measles, mumps and rubella vaccine at the Rockland County Health Department in Haverstraw, Rockland County, New York. Getty Images/Johannes Eisele