Implications of a 2005 Measles Outbreak in Indiana for Sustained Elimination of Measles in the United States

Published in Volume 355 (pages 447-55) of the New England Journal of Medicine, this article examines a measles outbreak which occured in Indiana in the United States - an outbreak caused by the importation of measles into a population of children whose parents had refused to have them vaccinated because of safety concerns about the measles, mumps, and rubella (MMR) vaccine.

Measles - a highly infectious viral disease that can cause a rash, fever, diarrhoea and, in severe cases, pneumonia, encephalitis and even death - was declared eliminated from the United States in 2000. However, this 2005 outbreak was caused by a 17-year-old unvaccinated girl who visited an orphanage in Romania on a church mission. (At the time of her travel, Romania had not reported a measles outbreak, but several months later, it reported more than 4000 cases). Specifically, approximately 500 persons attended a gathering at a church with the girl one day after her return to Indiana. Fifty or so of them lacked evidence of measles immunity, of whom 16 (32%) acquired measles (genotype D4, which is endemic in Romania) at the gathering. During the 6 weeks after the gathering, a total of 34 cases of measles were confirmed; of those, 94% were unvaccinated. Of the 28 patients who were 5-19 years of age, 71% were being home-schooled (the United States imposes compulsory immunisation of children in the "official" school system, but not those who are home-schooled). Vaccine failure occurred in 2 persons.

Although containment measures began after 20 persons were already infectious, measles remained confined mostly to children whose parents had refused to have them vaccinated. According to representatives of 6 families from the church, issues considered important in their decision to refuse the vaccine were media reports of the dangers of the vaccine (e.g., the purported association between measles vaccination and autism, as well as the perceived effects of the vaccine preservative thimerosal) and a preference for naturally acquired immunity. Ten families in the church congregation who declined vaccination had at least one family member who was eligible for the measles vaccine before the outbreak. Although 9 of these families still had members who were eligible for vaccination during efforts to control the outbreak, only 2 families agreed to vaccination - "even in the midst of an outbreak involving hospitalizations among their own community members."

The outbreak, which was the largest documented one since 1996, "created substantial health risks, and required a vigorous and expensive public health response." The authors observe that "In the United States, efforts to raise immunization rates have focused on improving preventive care for disadvantaged children, but different approaches may be necessary for populations such as this one, where belief systems, rather than access to health care, are the primary barrier to vaccination." They conclude that "The outbreak in Indiana shows that states, localities, and health care organizations need to implement more effective policies to protect persons traveling abroad, home-schooled children, and health care workers against measles and other vaccine-preventable diseases. In addition, to preclude the experience of those countries where vaccine-preventable diseases have become epidemic through the refusal of vaccination, better communication strategies are needed concerning the adverse events associated with vaccines."