[What you need to know to start the day: Get New York Today in your inbox.]

Public officials and health experts had given several warnings: Do not allow a student in school if they had not been vaccinated against measles.



Still, during New York City’s largest measles outbreak in a decade, a school in Brooklyn ignored that advice, resulting in one student infecting at least 21 other people with the virus.

The outbreak, at Yeshiva Kehilath Yakov in Williamsburg, is reigniting concerns that too many people in New York’s ultra-Orthodox Jewish communities are unvaccinated, as well as worries that measles would continue to spread after travelers arrived last fall from parts of Israel and Europe, where the virus was spreading.

City officials said they have struggled to increase vaccination rates in certain communities because of popularity of the widely debunked anti-vaccination movement, with parents declining vaccines for their children in fear that they increase the risk of autism.