The largest, documented measles outbreak to hit the United States in a decade infected 34 people in Indiana last year.
The vast majority of the infected were children whose parents had objected to immunization.
The Indiana outbreak “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,” wrote Amy A. Parker of the Centers for Disease Control and Prevention in Atlanta, and her associates.
The CDC team found that all but two of the 34 infections were in people who had never been vaccinated for measles; 30 of the patients (88%) were children aged 19 years or younger.
“Concern about adverse events, particularly related to media reports of a putative association between vaccinations and autism and of the dangers of thimerosal, appeared to play a major role in the decision of these families to decline vaccination,” Dr. Parker and her coinvestigators found.
The index patient was an unvaccinated 17-year-old girl who returned to her community after a church-mission trip to a Romanian orphanage, where she became infected.
Despite having prodromal symptoms, she attended a large gathering of church members the day after she got home. Eighteen patients were infected at the meeting (N. Engl. J. Med. 2006;355:447–55).
A school survey in 2004–2005 indicated that 98% of kindergartners and 98% of sixth graders in Indiana had received the recommended two doses of measles vaccine. But church officials estimated that a much smaller percentage of the 500 people who attended the Indiana meeting had been immunized, perhaps 90% or less.
“As long as some groups within a given community respond to spurious claims about the risks of the vaccine by refusing to vaccinate their infants, further outbreaks will occur,” commented Dr. E. Kim Mulholland, a professor of infectious disease epidemiology at the London School of Hygiene and Tropical Medicine, in a perspective that ran with the article (N. Engl. J. Med. 2006;355:440–3).