ATLANTA — The recent measles outbreak in San Diego—started by one child who imported the disease from Switzerland—reinforces the ongoing need to maintain high vaccination coverage, Dr. Jane Seward said at the winter meeting of the Centers for Disease Control and Prevention's Advisory Committee on Immunization Practices.
The unvaccinated 7-year-old boy, who had rash onset 12 days after returning to the United States, infected at least 11 additional children ranging in age from 10 months to 9 years. Four were infected in the pediatrician's office that the child had visited the day before he was taken to a hospital emergency department for high fever and generalized rash. Another two cases were the boy's siblings, while five attended his school.
One infant was hospitalized for 2 days for dehydration, and another traveled by plane to Hawaii while infectious, necessitating “quite a response” by public health authorities in that state, Dr. Seward noted.
All cases were unvaccinated, including eight whose parents had claimed personal belief exemptions. In fact, 10% of the 350 children in the index child's school—kindergarten through 9th grade—were unimmunized because of these sorts of such exemptions, said Dr. Seward, acting deputy director of the CDC's division of viral diseases, National Center for Immunizations and Respiratory Diseases. The other four children were unimmunized because three were less than 12 months of age and therefore too young to be vaccinated and the fourth had received her routine vaccination 6 days after the unrecognized exposure.
At the time of publication in the CDC's Morbidity and Mortality Weekly Report, the episode had necessitated quarantine of 70 children who lacked evidence of immunity (MMWR 2008;57:[early release]1–4).
In the 1950s, 3 million to 4 million cases of measles occurred annually in the United States, causing 4,000 cases of encephalitis, 150,000 respiratory complications, 48,000 hospitalizations, and 450 deaths. Since the implementation of a two-dose immunization schedule in the early 1990s, measles is no longer endemic in the United States. Today, all of the 50 or so U.S. cases reported annually were imported from developed countries including those in Europe and Asia.
There's good and bad news in the San Diego situation, Dr. Seward said. The bad news is that measles is highly infectious and still poses a threat, unimmunized people are still at risk, and many health care providers are not familiar enough with the disease to ensure appropriate infection-control practices in their offices. But on the upside, there were no cases in immunized children. “The wall of immunity held fast. … We need to remember we have an ongoing challenge to sustaining high vaccine coverage to maintain our current [measles] elimination status.”