There have been 654 cases of measles since an outbreak in Jewish neighbourhoods of Brooklyn that began in October 2018.
Officials said it was the highest number of cases in three decades, prompting state politicians in New York to revoke a religious exemption to mandatory school vaccinations.
In April New York City ordered all yeshivas in a Strictly Orthodox areas of Brooklyn to keep students out of class if they are not vaccinated against measles, or face a possible fine or closure.
Three other US states — California, Mississippi and West Virginia — have eliminated religious and personal-belief exemptions for vaccines.
Cases have been reported as far afield as Canada, where an outbreak in Montreal’s Chassidic community has prompted a vaccination programme for hundreds of children.
