Measles -- United States, January 1-April 25, 2008

SB Redd; PK Kutty, MD; AA Parker, MSN, MPH; CW LeBaron, MD; AE Barskey, MPH; JF Seward, MBBS; JS Rota; PA Rota, PhD; L Lowe, PhD; WJ Bellini, PhD

Disclosures

Morbidity and Mortality Weekly Report. 2008;57(18):494-498. 

In This Article

Editorial Note

Although ongoing measles transmission was declared eliminated in the United States in 2000[1] and in the World Health Organization (WHO) Region of the Americas in 2002,[2] approximately 20 million cases of measles occur each year worldwide. The 2008 upsurge in measles cases serves as a reminder that measles is still imported into the United States and can result in outbreaks unless population immunity remains high through vaccination. Among the 64 confirmed measles cases, prior vaccination could be documented for only one person.

Before introduction of measles vaccination in 1963, approximately 3 to 4 million persons had measles annually in the United States; approximately 400-500 died, 48,000 were hospitalized, and 1,000 developed chronic disability from measles encephalitis.[1] Even after elimination of endemic transmission in 2000, imported measles has continued to create a substantial U.S. public health burden; of the 501 measles cases reported during 2000-2007, one in four patients was hospitalized, and one in 250 died.[1]

Thus far in 2008, five U.S. residents and five visitors have been documented as acquiring measles abroad. Of these 10 persons, nine acquired measles in the WHO European Region. These importations likely are related to an increase in 2008 in measles activity in Europe. In Switzerland, approximately 2,250 measles cases have been reported since November 2006. The Swiss measles outbreak started in Lucerne, where the measles vaccination coverage level in children is 78%, and spread across the country, predominantly affecting children aged 5-15 years who were unvaccinated because of parental opposition to vaccination.** In Israel (which is included in the WHO European Region), a measles outbreak with approximately 1,000 cases is ongoing (Ministry of Health, Israel, unpublished data, 2008), and measles transmission is occurring in other European countries, predominantly among populations opposed to vaccination. This situation prompted travel advisories to be issued in the United States and Europe.†† Health-care providers should advise patients who travel abroad of the importance of measles vaccination and should consider the diagnosis of measles in persons with clinically compatible illness who have traveled abroad recently or have had contact with travelers.

The limited size of recent measles outbreaks in the United States has resulted from highly effective measles and MMR vaccines, preexisting high vaccination coverage levels in preschool and school-aged children, and a rapid and effective public health response. All children should receive 2 doses of MMR vaccine, with the first dose recommended at age 12-15 months and the second dose at age 4-6 years. Unless they have other documented evidence of measles immunity,§§ all adults should receive at least 1 dose. Two doses are recommended for international travelers aged ≥12 months, health-care personnel, and students at secondary and postsecondary educational facilities. Infants aged 6-11 months should receive 1 dose before travel abroad.[3] During a measles outbreak, the vaccination response should be guided by the epidemiology of the outbreak and the outbreak setting and might include offering 1 dose of measles or MMR vaccine to infants aged 6-11 months, offering the second dose to preschool-aged children provided that 28 days have elapsed since the first dose, and recommending 1 dose to health-care workers born before 1957 unless they show other evidence of immunity.

Patients with measles frequently seek medical care, and emergency departments are common sites of measles transmission.[4] To prevent transmission of measles in health-care settings, patients should be asked to wear a surgical mask (if tolerated) for source containment, airborne infection-control precautions[5] should be followed stringently, and patients should be placed in a negative air-pressure room as soon as possible. If a negative air-pressure room is not available, the patient should be placed in a room with the door closed. Measles cases should be investigated, patients isolated promptly, and specimens obtained for laboratory confirmation and viral genoptying. Case contacts without documented evidence of measles immunity should be vaccinated, offered immune globulin, or asked to quarantine themselves at home from the fifth day after their first exposure to the twenty-first day after their last exposure. Contacts with measles-compatible symptoms should be managed in a manner that will prevent further spread.[3,5]

Health-care personnel place themselves and their patients at risk if they are not protected against measles. In accordance with current recommendations, health-care personnel should have documented evidence of measles immunity¶¶ readily available at their work location.[3] If this documentation is not available when measles is introduced, major costs and disruptions to health-care operations can result from the need to exclude potentially infected staff members and rapidly ensure immunity for others.[6]

Many of the measles cases in children in 2008 have occurred among children whose parents claimed exemption from vaccination because of religious or personal beliefs and in infants too young to be vaccinated. Forty-eight states currently allow religious exemptions to school vaccination requirements, and 21 states allow exemptions based on personal beliefs.*** During 2002 and 2003, nonmedical exemption rates were higher in states that easily granted exemptions than states with medium or difficult exemption processes[7]; in such states, the process of claiming a nonmedical exemption might require less effort than fulfilling vaccination requirements.[8]

Although national vaccination levels are high,††† unvaccinated children tend to be clustered geographically or socially, increasing their risk for outbreaks.[6,9] An upward trend in the mean proportion of school children who were not vaccinated because of personal belief exemptions was observed from 1991 to 2004.[7] Increases in the proportion of persons declining vaccination for themselves or their children might lead to large-scale outbreaks in the United States, such as those that have occurred in other countries (e.g., United Kingdom and Netherlands).[10]

Ongoing measles virus transmission has been eliminated in the United States, but the risk for imported disease and outbreaks remains. High vaccination coverage in the United States has limited the spread of imported measles in 2008. Nevertheless, the measles outbreaks in 2008 illustrate the risk created by importation of disease into clusters of persons with low vaccination rates, both for the unvaccinated and those who come into contact with them.

**World Health Organization. Measles and rubella surveillance bulletin. Geneva, Switzerland: World Health Organization; 2008. Available at https://www.euro.who.int/vaccine/publications/20080401_1.

††U.S. travel advisories available at https://wwwn.cdc.gov/travel/contentmeasles.aspx. European travel advisories available at https://ecdc.europa.eu/health_topics/measles/080423_travel_advice.html.

§§Laboratory evidence of immunity, documentation of physician-diagnosed measles, or birth before 1957.

¶¶Documented receipt of 2 doses of live measles virus vaccine, laboratory evidence of immunity, documentation of physician-diagnosed measles, or birth before 1957.

***Institute for Vaccine Safety. Vaccine exemptions. Baltimore, MD: Johns Hopkins Bloomberg School Public Health; 2007. Available at https://www.vaccinesafety.edu/cc-exem.htm.

†††CDC. Statistics and surveillance: immunization coverage in the U.S. Atlanta, GA: US Department of Health and Human Services, CDC; 2008. Available at https://www.cdc.gov/vaccines/stats-surv/imz-coverage.htm.

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