Indiana Measles Outbreak Spurs Call to Toughen Vaccine Rules

ATLANTA, Aug. 3 -- Stricter vaccine rules for international travelers might have prevented an outbreak of measles last year in Indiana CDC public health workers suggested.

The outbreak affected more than 30 people and threatened the lives of three, according to a report in the Aug. 3 issue of the New England Journal of Medicine.

Requiring home-schooled children to receive recommended immunizations might also prevent future measles outbreaks, said Amy A. Parker, M.S.N., M.P.H., and colleagues, at the CDC's National Center for Immunization and Respiratory Diseases here.

The outbreak started on May 15, 2005, when an unvaccinated 17-year-old girl returned home to Indiana after a church-mission trip to Romania, where measles is endemic. The girl became infected with measles virus while visiting an orphanage there.

The day of her return, the girl attended a church gathering with about 500 people. The church itself had no position on vaccines, but a significant number of its members had refused to immunize their children against the measles because of rumored fears that the vaccine causes autism. These children were home-schooled.

Of the estimated 50 people at the gathering who had not been immunized, 16 (32%) became infected with measles that day. Another 18 people in the community became infected over the next six weeks, bringing the total up to 34.

During the course of the outbreak, a 45-year-old man and a six-year-old girl were hospitalized to undergo intravenous rehydration. In addition, a 34-year-old hospital phlebotomist, who had never received her second dose of measles vaccine, required ventilator support for pneumonia complications stemming from the measles.

In addition to the phlebotomist, vaccine failure also occurred in a 16-year-old attendee of the church gathering who had received both doses of the measles vaccine. However, nearly all (94%) of those who contracted the measles were unvaccinated. Most (88%) were under the age of 20.

"The outbreak was the largest documented outbreak in nearly a decade, created substantial health risks, and required a vigorous and expensive public health response," the CDC authors said.

The high rate of vaccine coverage in the state of Indiana (estimated at 98%) likely helped contain the outbreak and prevented an epidemic, they added.

The CDC's Advisory Committee on Immunization Practices (ACIP) recommends two doses of measles vaccine or proof of immunity (antibody titer) for people traveling abroad, but compliance is voluntary, the authors said.

Although every U.S. state requires two doses of measles vaccine for children to attend school, only one state, West Virginia, also requires home-schooled children to be immunized, the authors said.

"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," they concluded.

Editorialist E. Kim Mulholland, M.D., of the London School of Hygiene and Tropical Medicine, agreed that stricter rules for travelers would cut down on the spread of measles.

"Yet as long as measles continues to circulate in other parts of the world, cases will continue to be imported," Dr. Mulholland said. "And 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 even in industrialized countries."

Measles was declared eliminated in the United Sates in 2000, the culmination of a vaccine campaign that began in the mid 1960s, Dr. Mulholland said.

"Despite the vision of the public health officials in the 1960s, global eradication of measles remains a long way off. In the meantime, countries must strive to immunize as high a proportion of children as possible, using a second dose to minimize the risk of primary vaccine failure and improve coverage," Dr. Mulholland concluded.