Vaccination of Amish limited 2014 Ohio measles outbreak
Members of a mostly unvaccinated Amish community in Ohio helped limit the spread of the largest measles outbreak in the United States in more than 2 decades by eschewing tradition and getting vaccinated by the thousands, according to a new report.
The Amish population at the heart of the 2014 measles outbreak that infected hundreds of people across nine Ohio counties was less opposed to vaccination than Amish communities have been in the past, researchers wrote in the New England Journal of Medicine.
In addition, the Amish also were willing to avoid social gatherings where the disease could have spread further. The result was that the outbreak was all but contained to their community, but affected only about 1% of the nearly 33,000 Amish living there.
“Facing a significant health threat, many of the members of the Amish community followed the advice of local public health workers in an effort to protect their community and the larger non-Amish community,” study researcher Dwight J. McFadden III, MD, MPH, of the Holmes County (Ohio) Health Department, told Infectious Disease News. “Without this collaboration, we would not have been able to end this outbreak when we did, and it would have eventually been exported to many other states, infecting many other undervaccinated and highly vulnerable Amish communities.”
Communities at risk
Although the Americas recently were declared the world’s first WHO region to be free of measles, travel-related outbreaks still occur in the U.S. and are mostly associated with intentional vaccine refusal.
The Ohio outbreak originated in two unvaccinated Amish men aged in their early 20s who traveled to the Philippines to aid typhoon relief efforts before returning to Knox County. Some 383 people were reported to be infected between March and July 2014, all but three of them Amish. The strain of measles that circulated in Ohio matched a virus strain that was circulating simultaneously in the Philippines.
Before the outbreak, only an estimated 14% of people in the affected Amish households had received at least one dose of the measles-mumps-rubella vaccine, while coverage with at least two doses of MMR vaccine was 88% in the rest of the community, a high baseline coverage that probably limited the spread outside the Amish settlement, according to the report.
Although vaccination is not prohibited by Amish religion, participation in preventive health care is limited by personal and cultural beliefs, according to McFadden and colleagues.
“The magnitude and duration of the outbreak illustrate how communities that object to vaccination are at increased risk for the spread of measles and for potentially becoming a source of further transmission,” they wrote.
It was the longest sustained measles outbreak in the U.S. since measles was declared eliminated in the country in 2000, but it could have been much worse if the Amish had not collaborated with the local health departments, McFadden said.
“Without trusted local health departments working within the community to build relationships with vulnerable populations such as the Amish in this case, we may not have been able to stop the outbreak as quickly as we did,” he said.
The role of the Amish
McFadden said health officials were unsure how the Amish would respond to requests to get vaccinated and to avoid high-risk social situations such as church gatherings, weddings and work.
“We knew that if we had any chance of containing the measles, we had to increase vaccination rates rapidly, and we needed to have quarantine and isolation protocols,” he said.
In response to the outbreak, which occurred between March 24 and July 23, 2014, some 10,644 members in a community of 32,630 Amish in the Ohio settlement received at least one dose of the MMR vaccine, with 1,585 getting two doses.
Sixteen people who received the vaccine around their time of measles exposure emphasized the need to vaccinate as soon as possible during outbreaks, McFadden and colleagues wrote.
“To vaccinate as many people as were vaccinated in the short months that it was done is a real feat,” McFadden said.
Among the other epidemiological features of the outbreak as noted in the report:
- The median age of the patients was 15 years, but the age distribution of the outbreak changed from mostly adults to mostly children once members of the community began following isolation requests.
- The crude attack rate was 12 cases of measles per 1,000 Amish persons, with rates lower among those aged older than 39 years. The attack rate for measles in the U.S. is less than one case per million persons.
- No case patients were aged 55 years or older, supporting the statement that people born before 1957 have presumptive evidence of measles immunity.
- Sixty-eight percent of the overall transmissions occurred in households, but this also was a result of the containment efforts. Initially, church was a source of many exposures.
- The outbreak occurred during summer vacation when Amish school are closed, probably limiting its spread.
- Of the three people outside of the Amish community who were infected, all were epidemiologically linked to the Amish.
- Dengue was initially diagnosed in the men who returned from the Philippines; measles was only reported after a febrile illness with rash was noted among 12 other members of the community.
- Some 340 of the 383 case patients were unvaccinated; 106 of them received vaccination.
- The church-related group that organized the charity relief trip to the Philippines began vaccinating volunteers before their future trips.
Not immunizing relief workers ‘inexcusable’
McFadden said he did not want to simplify the relationship between the cooperation of the Amish and the curtailed outbreak.
“Not everyone who was vulnerable accepted vaccination, and I don’t believe that the outbreak convinced those in the community that are against vaccinations that all vaccinations are good,” he said. “But it did help to demonstrate to the community why we vaccinate, and enough people were vaccinated and listened to our instructions about isolation and quarantine.”
In a related editorial, David N. Durrheim, MB, ChB, DrPH, of the Western Pacific Measles Regional Verification Commission in Wallsend, Australia, said outbreaks of measles among undervaccinated populations such as the Amish community in Ohio can have value in identifying and characterizing immunity gaps.
But Durrheim called it “inexcusable” that relief workers who travel to areas where vaccine-preventable diseases circulate are not properly immunized.
“Every death from measles is a tragedy that should have been prevented,” Durrheim wrote. “Effective tools to achieve the elimination of measles are already available, and even more effective delivery methods, such as the use of microarray patches, are on the horizon. Every immunity gap should be filled.
“Because the measles virus has an uncanny ability to expose these immunity gaps, we should capitalize on this phenomenon and allow a careful understanding of measles outbreaks to be our guide as we progress toward the ultimate goal of measles eradication.” – by Gerard Gallagher
Disclosure: The researchers and Durrheim report no relevant financial disclosures.