Pertussis outbreak in an Amish Community: Kent County, Delaware, 2018

The Amish lead a very simplistic lifestyle free of modern conveniences. They have unique perceptions and beliefs regarding health and illness and generally do not adhere to conventional preventive measures such as immunizations, which can result in un- or under-immunized populations. Populations with low vaccination coverage are at greater risk of outbreaks compared to vaccinated populations as a result of low herd immunity. Over the past two decades, the Delaware Division of Public Health (DPH) has recorded three distinct outbreaks of pertussis in Delaware's Amish community. The third, and most recent, outbreak was detected in May 2018. DPH conducted an outbreak investigation in the Amish community to identify cases, estimate the burden of disease in the community, and implement control measures including vaccination, treatment, and post-exposure prophylaxis. Through the conduct of active surveillance activities, DPH interviewed 134 families and identified 181 confirmed and probable cases of pertussis. The majority of pertussis cases (77%) occurred among children ≤10 years of age, of which 87% were unvaccinated. DPH engaged the Amish community in meetings, distributed educational materials, and provided medication and vaccines in the community to encourage prevention and implement control measures. DPH officially closed the outbreak investigation on December 20, 2018 following three full incubation periods (63 days) without any new pertussis cases identified in the community.