This week the City of New York declared a public health emergency because of a measles outbreak that had been escalating since the fall in ultra-Orthodox communities in Brooklyn and finally reached the point of crisis. In December the Health Department had made an effort to contain the disease, ordering yeshivas and child care centers in affected neighborhoods to keep all unvaccinated children from going to school or day care. Then, in January, at least one yeshiva in Williamsburg ignored the mandate. This failure of compliance led to an eruption of dozens of new cases.

Like well-off bohemians who might send their children to Waldorf schools, where an anti-vaccination culture is baked in the warm ovens of so many sprouted-wheat snacks, many among the ultra-Orthodox resist the incursions of modernity. A distrust of immunization had long ago taken hold in some sectors of the Hasidic community, but this year various religious neighborhoods in Brooklyn were hit with a propaganda campaign meant to breed even more skepticism and fear.

As it happens, 2019 is turning out to be a record year for measles outbreaks, with 465 cases reported in 19 states, according to the Centers for Disease Control and Prevention. A vast majority of these have occurred in Brooklyn and in counties in upstate New York and New Jersey with substantial ultra-Orthodox populations. Approximately 115 cases, though, have been discovered in Michigan and Washington, among the 17 states in the country where it is possible to seek a “personal belief” exemption from otherwise mandatory vaccines for school-aged children, meaning that immunization essentially violates your parenting philosophy as if it were Fortnite or a bag of Cool Ranch Doritos.

Where there are no such vague clauses in vaccination law, there are typically exemptions available to those who claim that they oppose vaccination on religious grounds; 47 states have these, including New York. They are problematic for a number of reasons. First, there is virtually no canonical basis for vaccine avoidance among the world’s major religions, most of which came into being before Edward Jenner developed the first widely used vaccine, against smallpox, at the end of the 18th century. Rabbis since then have repeatedly stressed the importance of protecting children through vaccination. Regardless, religious waivers provide cover to those who resist vaccines simply because they chose to question established science.