A pretty cool trend, if you ask me.
But more to the point of this thread, this article is a good synopsis of what I've read in various sources...
Monkey, Rat and Pig DNA': How Misinformation Is Driving the Measles Outbreak Among Ultra-Orthodox Jews
..."The Vaccine Safety Handbook" appears innocuous, a slick magazine for parents who want to raise healthy children. But tucked inside its 40 pages are false warnings that vaccines cause autism and contain cells from aborted human fetuses.
"It is our belief that there is no greater threat to public health than vaccines," the publication concludes, contradicting the scientific consensus that vaccines are generally safe and highly effective.
The handbook, created by a group called Parents Educating and Advocating for Children's Health, or Peach, is targeted at ultra-Orthodox Jews, whose expanding and insular communities are at the epicenter of one of the largest measles outbreaks in the United States in decades....
"Vaccines contain monkey, rat and pig DNA as well as cow-serum blood, all of which are forbidden for consumption according to kosher dietary law," Moishe Kahan, a contributing editor for Peach magazine, said in an email.
Vaccines are often grown in a broth of animal cells, but the final product is highly purified. Most prominent ultra-Orthodox rabbis agree that vaccines are kosher, and urge observant Jews to be immunized.
Still, from enclaves in suburban Rockland County to the bustling streets of Brooklyn's Borough Park neighborhood, fliers tell the Hasidim to be skeptical of immunizations. On a recent Sunday evening, a four-hour conference call promoted to ultra-Orthodox families -- with call-in numbers for a variety of countries -- offered advice from speakers who were presented as experts in vaccine science....