THURSDAY, Oct. 20 (HealthDay News) -- The largest U.S. outbreak of measles to occur in 15 years -- affecting 214 children so far -- is likely driven by travelers returning from abroad and by too many unvaccinated U.S. children, according to new research.
The finding could highlight the dangers of a trend among some U.S. parents to skip the measles-mumps-rubella (MMR) vaccine for their children, out of what many experts call misguided fears over its safety.
Dr. Andrew Pavia, professor of pediatrics at the University of Utah and spokesman for the Infectious Diseases Society of America (IDSA), said, "The good news is that we are seeing introductions of measles that are being contained as small outbreaks."
Pavia credits containment to high levels of vaccination and the rapid response by public health officials. However, if an outbreak occurred in a "really susceptible population the outcome could be very different," he said.
"What would happen in an area with a lot of vaccine refusers? Then you might see a much larger outbreak," he said.
Several measles-related studies were unveiled at the annual IDSA annual meeting, currently being held in Boston.
In the first report, U.S. Centers for Disease Control and Prevention (CDC) researchers chronicled the nation's ongoing outbreaks in 2011.
Most of those sickened were not vaccinated against the disease, CDC researchers said.
Before the vaccine became available in the 1960s, some three to four million people contracted measles every year. Of those, 48,000 were hospitalized, 1,000 were permanently disabled and about 500 died, the CDC said.
Unfortunately, "we have experienced an increased incidence of measles this year," said Huong McLean, lead researcher and CDC epidemiologist. "Typically we see 60 to 70 cases a year, this year we have 214 as of Oct. 14."
Among those people infected, 86 percent were unvaccinated or their vaccination status was unknown. Thirteen percent were under one year old -- too young for vaccination.
Throughout the United States, 68 of the patients have been hospitalized, 12 with pneumonia.
Most of these cases occurred among people who traveled overseas to Western Europe, Africa or Asia, where vaccination rates are lower, and the disease is an ongoing problem, the researchers note.
McLean said that the vaccination coverage in the United states remains relatively high, about 90 percent. "However, measles is very contagious and can spread quickly in communities where people aren't vaccinated," she said.
"The vaccine is very safe and effective in preventing the disease," McLean said. The MMR vaccine, which protects against measles, mumps and rubella (German measles), is designed to be given to infants 12 to 15 months old with a second shot given when the child is four to six, according to the CDC.
The Minnesota Department of Health released figures on a state outbreak, which started in March with an unvaccinated child, aged two and a half , who had traveled to Kenya. The child attended a drop-in Minnesota child care center. Overall, 21 people were infected and 14 hospitalized.
"Health care providers together with public health and community leaders must address growing vaccine hesitancy to ensure high immunization rates in all communities," Pam Gahr, a senior health department epidemiologist, said in an IDSA news release.
Not only is measles highly contagious, it's also expensive to contain its spread, according a third meeting presentation.
Dr. Karyn Leniek, deputy state epidemiologist for the Utah Department of Health, said an outbreak occurred when one unvaccinated high school student, who had been to Europe, brought measles back with him.
Although only nine people became infected, the cost of containing the outbreak was about $300,000. Costs included infection control in two area hospitals and intervention by local and state health departments. Costs also included physician and staff time, vaccines, immunoglobulin and blood tests, according to the study.
Containing the outbreak meant contacting 12,000 people about possible exposure and quarantining 184 people, including 51 students. Of the teens not vaccinated, including the European traveler, six were unvaccinated due to personal exemptions.
"Personal exemptions include philosophical or any other unspecified non-medical exemption," the researchers noted.
"It is always a concern to have a large number of unvaccinated people in close proximity," Leniek said in an IDSA statement. "Our goal is to have as many people vaccinated as possible to protect those who cannot receive the vaccine and who are not fully immunized."
Another Thursday presentation centered on a large measles outbreak in Quebec, Canada: the largest since 1989, with 757 cases as of October 5.
That outbreak started with 18 people who traveled abroad, most to Europe. Among those infected, 505 had not been vaccinated or their vaccination status was not known, and 70 had received only one doses of the vaccine, according to the report.
"This outbreak is being fed largely on unvaccinated or undervaccinated people, but we were concerned that a significant number had received the recommended two doses of MMR vaccine," Philippe Belanger, an epidemiologist at Ministere de la Sant? et des Services Sociaux du Quebec, Montreal, said in the releases.
To keep measles at bay, Pavia said public health officials should be on the outlook for measles and the high level of vaccination needs to be maintained.
"The ongoing fear of the measles vaccine and the myths about measles vaccine and autism just won't go away -- and put us at continuous risk," Pavia said. One such myth, according to most experts, is that the shot might cause autism in children. That notion spread after a British researcher, Dr. Andrew Wakefield, published a study in The Lancet in 1998 claiming a link. The research was later discovered to be fraudulent, however, and the journal has since retracted the article.
Pavia stressed that when parents decide against vaccinating their child, their action may affect other kids, as well.
"Your child might get measles and do well. But if you are the one who brings measles back into the community and your child infects someone else in the classroom who can't be vaccinated because of being immunocompromised, you might be responsible for the death of another child or an infant who can't be vaccinated," he said.
For more information on measles, visit the U.S. National Library of Medicine.