Two-thirds of US children who contracted measles in recent years were not vaccinated because of their parents' personal beliefs, report health officials from the Centers for Disease Control and Prevention in Atlanta.
Before national measles vaccination was introduced, up to 4 million people got measles every year, they note in a report in The Journal of Infectious Diseases. In 2000, the US declared that measles had been eradicated within its borders, but the current report shows that infections continue to occur, largely due to "importation" of the infection from abroad and decisions by parents not to immunize their children.
While concerns had been raised that the measles-mumps-rubella or MMR vaccine caused autism, extensive investigation has shown that the shot has no relationship to whether or not a child will develop autism.
To investigate the pattern of measles outbreaks in the "post-elimination era," Dr. Amy Parker Fiebelkorn and colleagues looked at CDC data for 2001-2008. During that time, they found, there were 557 confirmed cases of measles and 38 outbreaks; on average, there were 56 measles cases each year and four outbreaks annually.
Forty-two percent of the infections had been contracted in one of 44 different countries, the researchers found. Infants and children 15 months old or younger were the most commonly infected among US residents.
During the study period, 285 of the measles cases among US residents, or 65 percent, occurred in unvaccinated individuals. And in 2004-2008, the researchers note, 68 percent of the patients who developed measles lived in the US and were not vaccinated "because of personal belief exemptions."
While overall rates of measles vaccination are high, with 91 percent to 93 percent of 19-to 35-month-olds having had at least one shot, "there are communities and counties where vaccine exemption rates are several times higher than state averages," the researchers say.
School immunization programs help improve immunization rates, they add, but some states allow home-schooled kids to be exempt. Forty-eight states allow religious exemptions and 20 allow for philosophical/personal belief exemptions.
Until measles is eradicated worldwide, the researchers say, people who travel abroad will run the risk of contracting the disease, while pockets of unimmunized individuals may fuel outbreaks.
Nevertheless, they add, the "record low numbers of reported measles cases and small, short-lived outbreaks" show that "measles elimination in the United States has been maintained."