The Disneyland measles outbreak in southern California has once again pitted health experts against a rising population of wealthy and educated anti-vaccinators who believe the vaccines themselves are dangerous. Cases of measles have surged in the U.S. faster than any time in nearly 20 years, including in California, in part because of successful anti-vaccination campaigns that cast doubt on the efficacy and safety of the vaccines. Widespread public health campaigns aimed at informing the public about the benefits of vaccination have often fallen short or been ignored, which can be partially attributed to many of the diseases the country vaccinates against being so rare that the public has all but forgotten that they ever existed.

The challenge health officials in California and other states have faced often comes down to informing the masses, experts have said. “I don’t think we do a good job of communicating the message of how vital these vaccines are,” said Natasha Burgert, a pediatrician in Kansas City, Missouri. “It’s not the facts that are going to help parents make their decisions. They make decisions about vaccines based on emotions."

Measles is a highly contagious disease and can spread very easily by air or through direct contact. It is also one of the leading causes of preventable death among young children. In 2013, there were 145,700 measles deaths worldwide, according to the World Health Organization. Between 2000 and 2013, there was a significant drop – 75 percent – in the number of measles deaths around the world because of vaccinations. Health experts have estimated that during that time, measles vaccinations prevented 15.6 million deaths.

Nationally, vaccination rates in the U.S. are relatively high, even when compared to other industrialized countries. Routine vaccines, including the measles-mumps-rubella, or MMR, and whooping cough vaccinations are at an all-time high, at around 90 percent nationally. In 2013, the states with the highest rates of infant MMR vaccinations were Mississippi at nearly 100 percent, followed closely by Maryland and South Dakota, both of which hovered around 98 percent. The states with the lowest vaccination rates for the same diseases were Colorado, Arkansas and Pennsylvania, each with a vaccination rate of about 86 percent, according to the CDC.

In California, vaccination rates among kindergartners have been steadily declining since 2008. At the same time, personal belief exemptions, which allow parents to bar their kids from getting vaccinated, have risen nearly a percentage point, according to the most recent report from the California Department of Public Health.

The measles outbreak at Disneyland in Orange County, California, this month has resulted in 67 confirmed cases. Forty-two of those patients had visited the park in December. The illness has since spread from the park to 11 counties in California, as well as Arizona, Colorado, Mexico, Oregon, Utah and Washington state.

In the wake of the outbreak, health officials in Orange County reached out to local schools through media releases and weekly status updates. “When this is over, we’ll have contacted thousands of people on the phone to let them know they may have been exposed,” said Matt Zahn, medical director for epidemiology for Orange County Public Health.

Some school districts took a more direct approach. A dozen students at Huntington Beach High School were told to stay home when they couldn’t produce proof that they were vaccinated.

Vaccine exemption laws allow parents to opt out of vaccinating their children for several reasons, including personal beliefs. The difficulty of getting a vaccine exemption varies by state. Nine states require just a parent signature. Twenty-one states and the District of Columbia require a health care professional to sign off, and 19 states require a notarized form or both a health care signature and a letter of explanation. States in which exemptions for personal beliefs are allowed have a rate of nonmedical exemptions that is 2.5 times higher than in states that accepted only religious exemptions, according to a 2012 study published in the New England Journal of Medicine. California requires a signature from both a parent or guardian and a health care professional.

Researchers have identified 39 so-called anti-vaccination clusters across California where non-vaccination rates were higher than normal. In those areas, which range in size from a few blocks to whole counties, the rate of parents citing personal beliefs for opting out of vaccinations was higher than the national average of 1.8 percent. In Marin County, which had the second-highest rate in the whole state of pertussis, commonly known as whopping cough, the rate was around 7.8 percent in 2012 – four times the national average of 1.8 percent.  

Part of the reason the anti-vaccination movement has gained momentum, experts have said, is that the campaign to eradicate diseases has largely worked. Decades of disease fighting virtually eliminated measles in the U.S. by 2000. Forty years earlier, about 3 million to 4 million Americans a year contracted the disease, according to the CDC.

The prevailing concerns parents often cite when it comes to vaccinations are related to autism and seizures. One in three Americans believes there’s some link between autism and vaccinations, according to recent polling, even though the study often cited has been widely discredited. Infant seizures, health experts have said, are actually fairly common and don’t have lasting consequences.

“We have new parents every day, and they hear these scary stories, but they don’t really know what the facts are,” said Amy Pisani, executive director of Every Child by Two, an advocacy group for public vaccine education. “They’re listening to their peers instead of their doctors.”

In many ways, the anti-vaccination information is simply more visible than pro-vaccination material, or competing in a way that hinders the message of governments.

“When families go on the Internet and search ‘vaccines,’ the first 10 websites you see are websites that question the importance of vaccines,” said Zahn. The best message that can be put out there is one that mixes science with anecdote. “The most visceral messages that you can have is someone who can say, ‘I got this disease and you don’t want to get it," he said.

Anti-vaccinators, however, argue that parents should have a right to do what they want with their kids. “I reject the ignorant label,” said Barbara Loe Fisher, co-founder and president of the National Vaccine Information Center, which bills itself as a vaccine safety organization but has frequently been cited as an anti-vaccination group. “People who are questioning the one-size-fits approach to vaccination … are by and large educated people.” She referenced “significant gaps” in the scientific literature about vaccinations, although health experts disagree.

Advocates of vaccination said the best thing parents can do is talk to their health care providers. “The idea that there are two sides to the story is just incorrect. When we make something into a controversy that isn’t, we give it credibility,” Jackie Kaufman, executive director of Vaccine Ambassadors, said over e-mail. “Healthcare providers and other experts in the field should be the ‘go to’ when discussing this topic.”

Last year in the U.S., there were 644 reported cases of measles, according to the CDC. “It is amazing that more than 50 years since the measles vaccine was first licensed, we continue to see this disease, especially in a country where vaccines are readily available,” Kaufman said.