Would-be theme park visitors discovered this week that Disneyland was far from the happiest place on earth after public health officials identified it as the source of a measles outbreak that has spread to at least 70 people in five states.
Most of the measles cases originated at two Disney theme parks in Anaheim, California, where the state’s public health department said on Wednesday that the majority of the people who caught it were unvaccinated. State epidemiologists think the outbreak began with a measles-infected visitor in mid- to late December, and urged people who haven’t been vaccinated to avoid theme parks, airports and other places where international travelers might visit.
The measles outbreak sheds light on a growing anti-vaccination movement, spread by parents and advocates, including former ABC television host Jenny McCarthy. As a result, parents may opt not to immunize their children because of religious beliefs or the fear that vaccines are linked to developmental problems such as autism. While every U.S. state requires children to provide proof of immunization before entering public school, most states offer parents religious exemptions from vaccinating their kids before enrollment, and 18 states allow them to skip vaccinations because of personal beliefs, according to the Johns Hopkins Institute for Vaccine Safety.
Scientists have thoroughly debunked the notion that autism is linked to vaccines, but certain U.S. states such as California, Oregon, Washington and Vermont have seen a rise in vaccine refusals from parents. A 2009 study in the New England Journal of Medicine found that state-level vaccine exemptions based on personal beliefs increased to an average of 2.54 percent in 2004 from 0.99 percent in 1991. More recent data show that personal belief exemptions among kindergartners have risen by nearly 1 percentage point since 2008 (PDF) in California, and a study published Monday in the journal Pediatrics identified a number of unvaccinated hot spots in California’s Bay Area, some where more than 10 percent of parents don’t vaccinate their kids.
Dr. Walter Orenstein, an associate director of the Emory Vaccine Center and a professor of medicine at Emory University in Atlanta, says there is no scientific evidence that supports parents’ fears about the adverse effects of vaccines. “We are constantly monitoring vaccines for safety,” he said. “It’s easy to make an allegation. The question is, what is scientifically valid? With the measles, mumps and rubella vaccine and autism, there are some outstanding scientific studies showing no link.”
Previous generations have seen the devastating effects of diseases like polio and are quick to vaccinate as a result, he said. “For many of these vaccine-preventable diseases, we’ve had good enough immunization coverage that people are not seeing that,” Orenstein said. “Young parents today haven’t seen cases of measles or meningitis. That fear factor is gone.”
Dr. Jay Gordon, a pediatrician in Santa Monica, California, says he believes in working with parents who are skeptical of vaccinating their children, and feels it’s safer to vaccinate children after 12 months because of the different immune responses of younger children. "I think that parents who would like to give vaccines at a later date or give them one at a time instead of six at a time should be supported, period,” Gordon said.
Still, Gordon cautions, communities need a high vaccination rate to preserve what is known as herd immunity, in which enough of a population is immunized that a disease can't spread. That way, people such as infants and pregnant women who can't take vaccines will still be safe.
As a result of this measles outbreak, Gordon says he has received a flood of calls from parents who had previously opted to delay but now want to vaccinate their children. With two doses of the MMR vaccine, between 95 and 99 percent of people are fully immunized within a week or two of their second shot.
Some other countries, especially Eastern Europe, have spottier vaccination rates, and in pockets of the U.S. where many parents choose not to immunize their children, all it takes is one family’s European vacation to start the spread of illness, according to Daniel Salmon, deputy director of the Johns Hopkins Institute for Vaccine Safety. “We don’t want to become like England, where people are dying of measles,” he said. “They’ve had serious gaps in vaccine coverage.”
He has studied the effect of vaccination exemptions in places like California, which in 2010 saw the worst outbreak of whooping cough since 1947, infecting more than 9,120 people and killing 10. He and his team discovered that the outbreak was directly linked to parents who had refused to immunize their children. “There was clear overlap there,” Salmon said.
Measles, a respiratory illness marked by a cough, runny nose and a rash, is highly infectious. It has been considered eliminated in the U.S. since 2000, meaning there have been so few annual cases (fewer than 300) that it’s no longer native to this country. That’s because of a strong push for MMR vaccination — measles, mumps and rubella — starting in the 1960s, when 3 to 4 million people would get measles each year, and about 500 died, according to the CDC.