Four years ago schools and day cares in western Washington embarked on an experiment. Too many kids in the state were going without needed vaccines that protect them against measles, whooping cough and other preventable diseases. Part of the problem, public health officials believed, was that parents lacked accurate medical information and held misguided beliefs that the vaccines were not necessary.



So they drafted some help—specifically, other parents who were trained by public health workers to answer common questions about vaccines’ risks and benefits. Armed with that knowledge and paid small stipends, these advocates went out to educate other parents. Many of the trained parents took to Facebook to spread the pro-vaccine word; others set up information booths at school and community events. “Over a period of three years we worked in a total of 21 sites including elementary schools, child care and preschools,” says Mackenzie Melton, immunization coordinator at WithinReach, a nonprofit that helped organize the program.



In the U.S. it was one of the only recent efforts to audition new methods for getting more parents to follow childhood vaccine recommendations. The majority of U.S. parents—83 percent—vaccinate with the recommended schedule but the gap in full vaccination has help set off the multistate measles outbreak that has gripped the U.S. since late last year. The spread only underscores how little researchers know about ways to boost vaccination rates among American communities. Scientific American interviewed nine experts studying or experimenting with ways to get parents to vaccinate their kids and analyzed the available peer-reviewed literature. The picture that has emerged elucidates a gap in public health knowledge and strategy when it comes to getting hesitant parents to accept vaccine recommendations for their kids. It also reveals that the sweet spot for intervention are parents that are on the fence, not those who have already decided against vaccines.



What works

Indeed, in the case of the Washington State peer educators program, researchers did not expect the vaccine-resistant parents to switch course—the hope was to inform parents who have not yet made up their minds. The program’s backers are still analyzing whether they achieved the short-term goals of raising awareness and affecting parental attitudes. Certainly, swaying more parents in low-vaccine communities to favor immunization would likely curb outbreaks, because so many vaccine-hesitant parents appear to live in clusters.



Recruiting community members to become pro-vaccine leaders is unique in North America but it is typical of what UNICEF (United Nations Children’s Fund) does with its partners in developing countries, notes Benjamin Hickler, a communication for development specialist at the fund. “Whether it’s breast-feeding, vaccinations or sanitation, we use peer networks and this kind of community-based approach, and it’s very effective.”



Yet in countries like the U.S. where vaccines are widely available, the science seems better at telling researchers what doesn’t work, rather than what does. One 2014 study from Dartmouth College researchers, for example, actually found that repeated pro-vaccine messages from public health agencies can actually backfire by creating more resistance to immunization among those with firmly held anti-vaccination beliefs. “This is an area where the science on the vaccines themselves is far ahead of the messaging and outreach,” says Brendan Nyhan, a professor at Dartmouth and author of that work.



One known way to improve vaccine coverage rates is for states to force compliance. Mississippi does not allow parents to exempt their children from receiving vaccines for personal reasons, and the state has the highest vaccination rates in the country. But eliminating exemptions for personal reasons is often politically unpalatable. Twenty states currently allow vaccination exemptions because of personal, moral or other beliefs, according to the National Conference of State Legislatures.



Money talks

But it may still be possible to achieve high vaccination rates and keep personal exemptions. In Australia parents can also choose to opt-out of vaccines, but measles vaccination coverage for one-year-olds is 94 percent, according to World Health Organization data. (The U.S. only has 91 percent coverage for measles vaccines at the same age.) So what’s different? One factor may be that the Australian government provides financial incentives for parents to get kids vaccinated—specifically, in the form of tax credits. Physicians, too, receive a small payment when children get vaccinations on schedule. Parents can still choose to forgo the inoculations and receive the tax credit, but their clinician would have to sign off on an exemption form (which some refuse to do).



The hassle of having to get that exemption “tends to sort out the hesitant from the more entrenched nonvaccinators,” says Julie Leask, a professor of public health at the University of Sydney. She believes the policy has been a major driver in helping to get kids vaccinated. The U.K., which has a measles vaccination rate of 95 percent, has also adopted its own financial approach. There, clinicians’ pay partly hinges on childhood immunization coverage.



Researchers, however, have yet to prove that financial incentives definitively boost the immunization rates. And even though something like the U.K. policy appears to work in that setting, “everything comes at a price,” says Daniel Salmon, deputy director at the Institute for Vaccine Safety at Johns Hopkins University. “A critic can argue that clinicians have a financial incentive to vaccinate” and are therefore not medically objective.



New strategies

Some researchers are still searching for approaches that can sidestep such critiques. Rutgers University psychology professor Gretchen Chapman studies what nudges push people to get seasonal flu vaccines. Her research has revealed that an effective way is to make it slightly more difficult to opt out of getting flu vaccines rather than to opt in. In one study she found that more individuals will accept a flu vaccination if they receive a message saying a flu shot appointment has already been scheduled (along with information on how to cancel it) than if they are told how to schedule an appointment.



The same default logic also appears to hold true with childhood immunizations. A 2013 study published in Pediatrics found that when parents were told that their child would receive a vaccine at their appointment instead of being asked which vaccines they wanted their kids to receive, more children ended up with their recommended shots. In fact, phrasing vaccine decisions as a choice rather than a decided course increased the odds that parents would refuse the recommended regime by almost 18-fold, says study author Douglas Opel, a professor of pediatrics at the University of Washington. That’s even after his team accounted for whether parents were known to be vaccine-hesitant and controlled for if the parent and clinician had a long-established relationship.



Rather than legislate opt-in rules, one community is trying a simpler approach that relies on the Internet, another top source of information used by parents. In Ashland, Ore., where the vaccine exemption rate was almost 30 percent last year and climbed as high as 66 percent in one private school (meaning that parents of 66 percent of kids had delayed or refused at least one recommended vaccine), public health workers and community members built a Web site (Ashlandchild.org) detailing the risks and benefits of vaccines. That site largely replaced the community education nights and peer-to-peer education projects that town had going for years. “We were just feeling like we weren’t getting much accomplished. Maybe we didn’t figure out the right way to break in but we felt as if our energies would be better served by trying to do this through the internet,” says Jim Shames, medical director for Jackson County Health and Human Services in Oregon.



Information delivered via a Web site may be effective but the science is perhaps clearest on one thing: In the U.S. what happens in the doctor’s office matters. Health care providers are one of the most important sources of information in decisions about childhood vaccines, according to surveys of parents. Unfortunately, physicians have no clear script for what to say. Parents that are hesitant to have their children receive inoculations are not all the same nor are there that many of them. Resistance to vaccination usually boils down to fears of long-term harm to their child or pain to children given so many shots.



Salmon, the Johns Hopkins researcher, hopes to move more people into the pro-vaccine camp by starting such conversations between health care workers and parents earlier—even before a baby is born. In November he and his colleagues kicked off a five-year, multimillion-dollar study with pregnant women. “We are focusing on obstetric providers and pregnant women. I think targeting pregnant woman is a really good idea—especially first-time moms, because they may not have made up their minds,” he says. Their tablet-based intervention hinges on women filling out a survey with demographic information and underlying attitudes, then they receive targeted videos and messages (for example, a Latina woman will get a video of a Latina woman talking to her about the safety and importance of getting her children vaccinated).



A generation of resistance

The need for new strategies to boost vaccination rates may come as no surprise considering that the current generation of parents may not have ever seen the first-hand dangers of measles and other preventable diseases. And without personally witnessing those diseases, parents may be more receptive to poor information, especially when readily delivered through social media or slick Web sites. “It’s become very difficult, especially because of how sophisticated anti-vaccination Web sites have become, to distinguish between the global scientific consensus of experts and these sites that, for a number of reasons, question that expertise, recast it as a conspiracy with Big Pharma or say this is about freedom versus the state,” Hickler says.



Modifying those Web sites to help dispel such misinformation is one approach that may provide a starting point for the U.S., he says.* In Australia, for example, the government used consumer protection laws to make at least one anti-vaccination network change its Web site name and more clearly state its vaccine position so parents would know what they are getting. Such an approach could be a lever that wouldn’t “impinge on individual freedom but help vaccine-hesitant parents navigate the conflicting advice out there,” he says.



Experts agree on at least one long-term approach: getting today’s kids onboard with vaccination. Once they learn about the safety and importance of childhood inoculation then perhaps anti-vaccination will not be as big of an issue when they have their own kids.

*Clarification (2/19/15): This sentence was edited after posting to more precisely describe one approach to dispelling misinformation on Web sites.