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MONSEY, N.Y. — An ultra-Orthodox rabbi falsely described the measles outbreak among Jews as part of an elaborate plan concocted by Mayor Bill de Blasio of New York to deflect attention from “more serious” diseases brought by Central American migrants.

A pediatrician questioned whether Jews were being intentionally given “bad lots” of vaccines that ended up giving children a new strain of the virus. And Andrew Wakefield, the British doctor whose study linking measles vaccines with autism was widely discredited and condemned, appeared via Skype to offer an almost apocalyptic vision of a world in which vaccines were giving rise to deadlier immunization-resistant diseases.

“We Hasidim have been chosen as the target,” said the rabbi, Hillel Handler. “The campaign against us has been successful.”

Since the measles outbreak began last fall, the health authorities have embarked on a sweeping and exhaustive campaign, repeatedly urging people to get vaccinated and fighting the spread of misinformation. They have made special efforts in the ultra-Orthodox communities of Brooklyn and Rockland County, N.Y., where the disease has been spreading most quickly.