WASHINGTON, D.C. As the measles-mumps-rubella (MMR) vaccine celebrates its silver anniversary, the United States is reporting record low levels of measles, and school-aged children are trying to figure out what exactly are these diseases.
The combined MMR vaccine (Merck & Co.) was licensed 25 years ago as an attempt to facilitate vaccine administration and keep immunization rates high.
The vaccine was successful; a study by the Centers for Disease Control and Prevention (CDC) estimated that during the 25 years that the vaccine has been in use, it has saved $34.6 billion in direct and indirect medical costs and 24,600 lives.
Meanwhile, the number of reported measles cases in the United States continues to fall. A record low of 301 confirmed measles cases were reported during 1995, according to the CDC. This figure represents a 69% decrease from the 963 cases reported during 1994, and is under the previous historic low of 312 cases reported during 1993.
The trend toward cases among older age groups continued. During 1995, 39% of cases occurred among people 20 years of age or older; during 1994, 24% of cases were in this age group.
"The low number of cases and shift in age distribution highlight the effectiveness and improved implementation of the recommendations of the Advisory Committee on Immunization Practices to provide the first dose of MMR [vaccine] at age 12 months to 15 months and to give a second dose of measles-containing vaccine, preferably MMR, at age 4 to 6 years or 11 to 12 years," the CDC noted in its report.
Of the 301 confirmed cases in 1995, the CDC obtained the immunization status of 62 people. Of those, 89% (55 people) had received at least one dose of measles-containing vaccine on or after their first birthday and 14 or more days before onset of symptoms. The remaining seven people whose vaccination status was known (11%) were considered unvaccinated or inadequately vaccinated because they had received vaccine less than 14 days before the onset of symptoms or before their first birthday. Only five people (8%) had received two doses of measles vaccine.
International importations accounted for only 33 cases (11%), with another 11 cases epidemiologically linked to imported cases. Austria, Belgium, Canada, China, Costa Rica, Egypt, France, Germany, Italy, Japan, Malaysia, Pakistan and The Philippines were the countries of origin.
Twelve states reported 19 measles outbreaks (defined as a cluster of three or more epidemiologically linked cases) during 1995. These outbreaks accounted for 74% of all cases. Genomic sequencing of isolates revealed that none of the outbreaks were linked to importations.
As immunization levels rise and disease incidence drops, vaccine-preventable diseases are becoming a thing of the past. A recent survey commissioned by Merck & Co. found that most children surveyed said they have never even heard the names of some diseases. One child admitted, "To get into the sixth grade we had to have measles, mumps and rubella shots. I don't really know what they are."
Word recognition seemed to be inversely related to the success of immunizations. For example, of 600 children between 8 and 12 years, more than 80% had never heard of rubella; of those who had heard of it, only 3% knew what the word meant.
Only 44% of those surveyed recognized the word "polio," and fewer than half could define it. Measles had the highest recognition, with 70% of the children surveyed being able to define it. The definitions, however, were often vague: "Little weird bumps like chickenpox, only worse."
In contrast, almost all of the children were familiar with chickenpox, with 95% reporting that they knew what the disease was. The first chickenpox vaccine became available last February.
Overall, the children accepted vaccines as important, although their understanding of what vaccines do was shaky; for example, one child described vaccines as "like some kind of deodorant or something like that." Other children were closer to the target, describing vaccines as "shots [that] give you some of the germs so you do not get the real thing."
For more information see:
- CDC. Measles United States, 1995. MMWR. 1996;45:305-7.
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