Federal health officials are urging some adults to get revaccinated against the measles amid the worst outbreak in 25 years, even though most should be protected.
The measles outbreak is at its highest level in the U.S. since 1994, with 704 confirmed cases so far this year, mostly among unvaccinated children, according to the Centers for Disease Control and Prevention. The disease is one of the most contagious in the world. Most people are vaccinated with the measles, mumps and rubella shot that's 97% effective when given both doses.
"Most adults are protected against measles, that's what the science says," Dr. Nancy Messonnier, director of the CDC's National Center for Immunization and Respiratory Diseases, said on a call with reporters Monday.
People born before 1957 are assumed to have had the disease and therefore be immune to it. The first measles, mumps and rubella shot in 1963 was considered ineffective and replaced with a new formulation in 1968.
Less than 1 million people were given the old vaccination over those five years, according to the CDC.
People vaccinated between 1963 and 1989 likely received only one dose of the modern vaccine. Updated guidelines call for two doses, though the CDC says one dose is still about 93% effective. Anyone born after 1989 likely received two doses.
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The CDC says adults who are going to be in a setting with a risk of measles exposure should find out whether they were vaccinated. Examples include people who are traveling internationally, working in health care, studying at universities or living in communities where outbreaks are occurring.
"We're really urging those adults to talk to their health-care provider to make sure that they're protected against measles," Messonier said. "But other adults should be reassured that the data really, really strongly supports that they are already protected against measles."
People who know they received the old vaccine should talk to their doctor about getting revaccinated with the current version, the agency says. If they aren't sure, they can ask their doctor to perform a blood test to see if they're immune or they can receive a dose of the modern vaccine, the CDC says.