A group of US parents filed suit on Monday against the New York City Department of Health to block an emergency order requiring measles vaccinations for everyone in four ZIP codes in the Williamsburg neighborhood of Brooklyn.
The threat of measles - and the opposition to vaccination - isn't coming from the hipsters who populate some parts of the neighborhood.
The target is a community of mostly Hasidic, haredi (ultra-Orthodox) Jews, who have refused vaccination, citing religious reasons, and who are now caught in the middle of a measles outbreak that city health officials fear could spread fast and dangerously. One yeshiva's preschool programme has already been closed as a health hazard.
Forced vaccination is a classic instance of a situation where the courts have to balance individual liberties against the public interest. The US Supreme Court's jurisprudence on the topic goes all the way back to 1904.
Under existing law, there is strong reason to think the city will win and will be able to fine refusers $1 000 in an effort to compel vaccination.
What makes the current case especially fascinating is that the refusal to vaccinate isn't simply that of isolated individuals who question the health value and assert a fundamental right to be free of bodily intrusion by the state.
The Williamsburg Jews who are refusing vaccination live in a highly concentrated community. Medically speaking, that makes them more dangerous than anti-vaccination activists spread thinly across the country - because an outbreak can infect a whole community and then spread outward.
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However, at the same time, the community's claim to be free of vaccination doesn't rest solely on the right to be left alone, but could also be grounded in a right to the free exercise of religious liberty.
Measles isn't a trivial disease. According to the Centers for Disease Control and Prevention, "as many as one out of every 20 children with measles gets pneumonia". Roughly one child in a thousand who gets measles will develop encephalitis that can produce convulsions, deafness or intellectual disability. Somewhere between one and two out of every thousand kids who get the disease die from the complications.
From an economic perspective, a 2017 paediatric modelling study found that a 5% reduction in measles, mumps, and rubella vaccination coverage resulted in a threefold increase in annual measles cases, with an additional US$2.1m (about R29m) in public sector costs.
According to the authors, small declines in vaccination coverage could have "substantial public health and economic consequences".
The vaccine is fairly effective, but not completely so - and that is the major source of the problem. A single dose is 93% effective; two doses raises that rate to 97%. That means even a vaccinated population can be vulnerable to getting the disease from people who are infected.
It follows that the people who don't vaccinate themselves or their children for measles aren't just endangering themselves. They're also imposing a spillover effect on the rest of the population that is vaccinated - and that could still become infected in an epidemic.
In the early 20th century case of Jacobson v. Massachusetts, the Supreme Court upheld a compulsory vaccination law, explaining that the Constitution "does not import an absolute right in each person to be, at all times and in all circumstances, wholly freed from restraint. There are manifold restraints to which every person is necessarily subject for the common good. On any other basis organised society could not exist with safety to its members".
Justice Oliver Wendell Holmes referred to this case in his famous dissent in the contemporaneous case of Lochner v. New York, using vaccination to illustrate his point that the Constitution doesn't create a purely libertarian framework of government.
Today, courts would typically balance the constitutional interests by saying that the state has a compelling interest in public health, but that its actions compelling vaccination must be narrowly tailored to the public health need.
The challengers to the current New York order are claiming that the vaccination order is arbitrary and capricious because it doesn't provide enough detail about the current measles threat, instead simply stating the number of measles cases have been documented since September. (That number is now at 329 according to the Department of Health; others have also been infected in haredi communities in Rockland County, north of the city.)
They also say there's no detailed plan for forced vaccination and that the vaccines could harm children and adults. In addition, the challengers say that the order violates New York's law on religious exemptions and violates their equal rights.
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Legally, these challenges don't seem sufficient to block the vaccination. The public health risks create a compelling state interest, and there isn't a narrower solution than forcing vaccination.
Culturally, however, a community that sees its refusal to vaccinate as religious might be difficult to compel. Closing schools might be medically necessary, but it also could have the effect of galvanising opposition.
On the other hand, nearly all mainstream Orthodox authorities consider vaccination not only permissible under Jewish law but even arguably mandatory as a health measure.
One solution to the outbreak could therefore be for the leading rabbis of the Williamsburg community - especially the two Satmar grand rabbis - to require vaccination as a matter of Jewish law. Indeed, a mainstream newspaper within the community has called for the refusers to stop believing in vaccination "myths".
The law of New York State is one thing. But the law of God is another, and is more likely to generate immediate obedience in the relevant community.
In the meantime, ordering compulsory vaccination could be a justifiable measure - if it works.