Measles Up in the U.S.

The CDC released a report this week detailing an increase in measles cases this year. From January to July there have been 131 cases all around the U.S. One hundred twenty three of those are U.S. residents and 112 were unvaccinated--63 of them for religious or philosophical reasons.


The report reminds us of the importance of immunization.

In the United States, measles caused 450 reported deaths and 4,000 cases of encephalitis annually before measles vaccine became available in the mid-1960s (1). Through a successful measles vaccination program, the United States eliminated endemic measles transmission (1). Sustaining elimination requires maintaining high MMR vaccine coverage rates, particularly among preschool (>90% 1-dose coverage) and school-aged children (>95% 2-dose coverage) (7). High coverage levels provide herd immunity, decreasing everyone's risk for measles exposure and affording protection to persons who cannot be vaccinated. However, herd immunity does not provide 100% protection, especially in communities with large numbers of unvaccinated persons. For the foreseeable future, measles importations into the United States will continue to occur because measles is still common in Europe and other regions of the world. Within the United States, the current national MMR vaccine coverage rate is adequate to prevent the sustained spread of measles. However, importations of measles likely will continue to cause outbreaks in communities that have sizeable clusters of unvaccinated persons.

It's also important to remember that vaccination does not always confer immunity; a certain percentage of vaccinated people fail to mount a protective immune response. In fact, recently a co-worker told me that they had to get the MMR vaccine as an adult because even though they were vaccinated as a child, lab tests failed to find antibodies against measles.

MMWR Weekly: August 22, 2008 / 57(33);893-896

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