A study of the largest rubella outbreak in the U.S. in the last five years found that those hardest hit were young children in daycare and workers in crowded meatpacking plants and their household contacts. In addition, seven pregnant women were among those infected with the disease, and at least one of their children was born with congenital rubella syndrome (CRS). The study was published in the December 6, 2000, edition of the Journal of the American Medical Association (JAMA).
Although overall immunization rates in the area (Omaha, Nebraska and the surrounding community, including sections of Iowa) were high (90.2% of children 19-35 months of age in Nebraska had been immunized against rubella), pockets of unimmunized children and adults allowed the disease to spread throughout the community. The outbreak resulted in 125 cases of rubella from March-August, 1999. The high overall immunization levels in the community kept the outbreak from spreading widely among the susceptible population.
Those infected were mostly workers in meatpacking plants and their family contacts who came to the U.S. from Latin American countries where the rubella vaccine is not part of national immunization programs. However, over 10% of the cases occurred among US-born children younger than the recommended age of immunization who attended two community day care centers. Although rubella immunization is required for daycare entry in Nebraska, the cases of disease all occurred in classes where children too young to receive the vaccine were grouped together. No infections occurred among people who were immunized against rubella.
The most serious effect of the outbreak was the birth of a child with congenital rubella syndrome (CRS), a syndrome that occurs in infants born to mothers infected with rubella early in pregnancy. The affected infant was born deaf and had a heart defect and a low platelet count. In addition to these disorders, this syndrome can also include mental retardation, eye defects, and diseases of the liver and the spleen. Overall, the number of CRS cases in the U.S. has fallen from a high of 20,000 in 1964-65 to about five per year today.
Because it is possible that additional pregnant women who were susceptible to rubella were exposed during this outbreak, the full number of CRS cases resulting from it is not yet known.
Dr. Louis Z. Cooper, an expert on rubella, member of the National Network for Immunization Information Steering Committee, and president-elect of the American Academy of Pediatrics, noted that 'This outbreak and a similar one in New York share the unfortunate consequence of children born with CRS. We must strengthen our resolve to close the loopholes in our rubella immunization programs, and insist that rubella immunization be included in the efforts now being devoted to eradication of measles in the Western Hemisphere.'
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