(JTA) — New York City’s info page on an ongoing measles outbreak could not be clearer: “Most of these cases have involved members of the Orthodox Jewish community,” it says.

But less clear is cause of the outbreaks, in heavily Orthodox neighborhoods of Brooklyn and Rockland County. Officials say low immunization rates in Rockland County and Brooklyn are to blame, and have tried to force residents to vaccinate. Orthodox organizations like Agudath Israel of America acknowledge that there are pockets of resistance to vaccination in those communities.

But they say overall vaccination rates for Orthodox Jews are in line with the general population and vaccination is the “clear societal norm” in the community.

State statistics show, however, that Rockland County’s immunization rates are significantly below the 96 percent goal set by the state Health Department. And more than 20 Orthodox schools in Rockland and Brooklyn had more than 10 percent of kids claiming a religious exemption from vaccination.

To be sure, a low vaccination rate isn’t the only issue at play. A Rockland County official told the Jewish Telegraphic Agency that other factors have contributed to the disease’s spread among Orthodox Jews. Orthodox Jews tend to live in close quarters with large families, and have a high rate of interpersonal interaction — for example, men gather for prayer at synagogue three times a day. The official said Orthodox Jews tend to travel overseas more often that other residents, which could bring measles cases from Israel or Ukraine, where cases have been reported.

That argument was echoed by Dr. Daniel Berman, who specializes in infectious disease, and Prof. Awi Federgruen of the Columbia University business school, who is active in efforts to encourage immunization. According to their analysis of public data, published in the New York Daily News, Orthodox schools in Brooklyn had an unweighted average vaccination rate of 96 percent. That’s higher than the 95 percent vaccination rate experts recommend in order for a community to be collectively immune from the disease.

“If you’re dealing with a community or area where there’s very intense and frequent interactions between individuals, there’s going to be much more of a force to propagate the epidemic,” Federgruen said in an interview. “And in Orthodox Jewish communities there are two factors: They live in areas with very high densities in population, and their lifestyle, the way they conduct themselves, people are interacting with each other physically in many ways.”

New York City declared a public health emergency in April, and required people in four heavily Orthodox Brooklyn ZIP codes to vaccinate. In March, Rockland County, home to the largely Orthodox city of Monsey, declared a state of emergency and barred unvaccinated kids from public spaces. The order was later rescinded.

At the time of the order, less than 73 percent of Rockland County was vaccinated. Owing to a series of free vaccination clinics, that rate has since crept up to around 77 percent, according to New York State data.

New York City has also shut down one Orthodox school for not providing immunization records to the state.

And some individual schools in Brooklyn and Rockland have low vaccination rates. According to data from the State Department of Education, more than 30 Orthodox schools in Rockland had immunization rates lower than 90 percent last year. In Brooklyn, the number was more than 20.

A bill in the State Assembly seeks to outlaw any exemption to vaccines aside from one mandated by a doctor — in other words, no religious exemptions.  The legislation, introduced in April, is spearheaded by two Jewish lawmakers.

Assemblyman Jeffrey Dinowitz, who represents part of the Bronx, said the current law is unclear as to whether schools are generally required to accept religious exemptions. For example, the New York State Department of Education recently forced the Shulamith School for Girls in Cedarhurst, New York to accept a student’s religious exemption from vaccination, according to the Five Towns Jewish Times. The school sought to block the student, saying that, contrary to the exemption, Jewish law requires vaccination.

Dinowitz told the Jewish Telegraphic Agency that he’s pushing to outlaw those and other non-medical exemptions because unvaccinated kids could put those who are immuno-compromised at risk.

“If someone has a legitimate medical reason to not get vaccinated, those people are exposed in a very significant way when there’s an outbreak,” he said. “I would never tell people how to practice their religion. It’s about health. It’s not about religion.”

A handful of rabbis, activist parents and vocal outsiders have been spreading anti-vaccination messages among Orthodox Jews, in public events, conference calls and social media. The organized Orthodox community, however, is supporting the effort to vaccinate. Agudath Israel of America has urged the community to vaccinate and cautioned against anti-Semitism due to the outbreak.

“[C]ountless rabbinical figures and leaders, including leading rabbis in the Agudath Israel movement and doctors serving these communities, have repeatedly encouraged vaccination in the strongest possible terms,” reads an April statement by the group.

The official in Rockland, speaking on background per local government policy, said that officials met with 100 Orthodox community leaders in October to try to stem the outbreak.

“If people think this is some kind of Jewish problem, it’s not,” Dinowitz said. “Leaders in the Orthodox community are advising people to get vaccinated because they understand that this can save lives.”