"Members of certain traditional reformed (bevindelijk gereformeerden) Christian denominations in the Netherlands, founded in the 1570s CE, have a tradition of declining immunization that dates back to concerns about adverse events after smallpox vaccination from 1823 onward. These communities were the epicenters of paralytic poliomyelitis, measles, congenital rubella syndrome, and mumps outbreaks between 1971 and 2008. Members of these denominations have familial and cultural ties to associated Christian communities in other countries (e.g., Canada, United States), where immunization rates may also be low. These ties have resulted in international transmission of vaccine-preventable diseases (e.g., measles, poliomyelitis, rubella) with multiple outbreaks in locations otherwise free of circulating disease."