Public Trust in Vaccines: Defining a Research Agenda

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Public Trust in Vaccines

From a public health perspective, the story of the twentieth century was, in many ways, the story of the success of vaccines. Smallpox, once a horrific scourge, was targeted by a global campaign that culminated in eradicating the disease in 1977. Today, the endgame of polio eradication is playing out in a small handful of nations where the disease remains endemic. In the United States, mandatory school vaccination laws have led to the virtual elimination of many deadly infectious diseases, including diphtheria, measles, mumps, polio, rubella, and Haemophilus influenza type b meningitis.

Looked at in one light, the country seems well positioned to continue these successes: The vast majority of parents in the United States immunize their children in accord with the recommended vaccine schedule. What’s more, national surveys indicate that a majority of parents whose children are not fully vaccinated support immunization but are poorly served by the health care system due to factors including lack of access to primary care, lack of insurance coverage, inadequate medical treatment and follow-up, and failure to enforce school-entry immunization requirements.7 (Addressing these issues will require fundamental changes in health care practices in this country and were therefore outside the scope of the Academy workshop.)

That leaves us with parents who are deliberately deferring or declining vaccines. Any clear-eyed assessment of the situation needs to acknowledge that their numbers are going up, not down. The results of this disturbing reality can be seen in costly outbreaks in communities with high numbers of deliberately unvaccinated children. In 2011, the nation experienced its largest number of individual measles cases (222 individuals) and outbreaks (17) since 1996; this is especially notable because the World Health Organization (WHO) declared measles eliminated from the United States in 2000. The index case in virtually every one of those recent outbreaks was an individual who was either deliberately unvaccinated—often a U.S. resident travelling abroad—or of unknown vaccine status.8 We need only look to France to see how quickly a seemingly contained disease can spiral out of control: In 2007, there were 40 reported cases of measles infections in that country. That figure jumped to 600 in 2008—and rose to more than 15,000 in 2011.9 Six of those cases resulted in death. Translating that rise to a population the size of the United States’ gives you more than 70,000 measles infections—and an estimated public sector cost of hundreds of millions of dollars.

The recent measles outbreaks in the United States and Western Europe are especially tragic because the MMR vaccine is overwhelmingly effective, which means virtually every single one of those cases could have been prevented. (Measles continues to claim some 158,000 lives annually, or about 430 lives every day, with most victims under the age of five. More than 95 percent of deaths occur in low-income countries with weak public health infrastructures.10)

And it is not just measles that is on the rise: In 2012, 48,277 cases of pertussis (whooping cough) were reported to the federal Centers for Disease Control and Prevention (CDC)11—the largest number in more than half a century, up from a modern low of about 1,000 cases in 1976.12 In developing countries, hard-won advances can vanish in a blink of an eye: After one state in Nigeria ceased universal polio immunization in 2003 because of spurious fears that the vaccine was being used to sterilize Muslims, the disease was reintroduced to twenty previously polio-free countries within three years.13

Research has clearly shown that parental attitudes toward vaccines fall along a continuum ranging from total acceptance to total refusal. When we define vaccine-hesitant parents not only as those who selectively vaccinate or delay some vaccines but also as those who have some misgivings about vaccines, a substantial number—between 20 and 30 percent—end up in this category.14

Today, the term “vaccine hesitancy” has gained acceptance, a shift in terminology that reflects not only this more nuanced understanding of parents’ positions, but also the importance of engaging and supporting those whose attitudes are not on one end of the spectrum or the other. Constructive dialogue between providers and parents can promote informed decision-making and help public health professionals better understand the concerns underlying vaccine hesitancy.15



Recent history shows the devastating effects of inaccurate information about vaccines. In 1998, press coverage of British physician Andrew Wakefield’s specious claims linking the MMR vaccine to bowel disease and autism caused public confidence in the vaccine to plummet. In England, MMR coverage rates dropped from nearly 93 percent in 1997 to 79.9 percent in 2003–2004.

And once doubt is planted, it is hard to uproot. In a 2011 survey taken immediately after the Wakefield study was retracted and Wakefield was accused of fraud, 27.9 percent of respondents said they still believed there was a link between vaccines and autism. In a stark illustration of the fact that simply restating a discredited fear can cause people to believe it is true, 5.6 percent of respondents said they were convinced that there was a link between vaccines and autism only after the news reports discrediting Wakefield’s study as fraudulent were aired.16

What else drives the vaccine confidence gap? Surveys and studies point to a myriad of reasons that parents request non-medical exemptions. Some are so unfamiliar with the diseases vaccines protect against that they conclude the vaccines themselves are unnecessary. Others cite concerns with vaccine safety broadly or rare vaccine side effects specifically, while questioning the efficacy of giving vaccines to healthy people in the first place. Some believe that vaccines overload children’s immune systems, or that “natural immunity” is preferable to vaccine-induced immunity; others believe that their children can avoid vaccination because a high enough percentage of the population is vaccinated to keep a given disease at bay. (Choosing not to vaccinate for that reason was described by one popular anti-vaccine doctor as “hiding in the herd.”17) Some parents cite their belief in alternative medicines; others are distrustful of the medical system, science, or anything recommended by government in general.18

On a more individual level, social science has shown that individuals have different styles of decision-making. Some parents accept social norms; others are more apt to rely on doctors, parents, or friends for advice. There are also those who scour the primary academic literature in an attempt to understand the science behind vaccines.19

It is also important to remember that decisions about vaccination are not made at a single point in time. Many parents have indicated that they began mulling the issue even before deciding to have a child. Pregnancy—a time of active information seeking—appears to be an especially formative time for thinking about vaccination.



As experts focus on the reasons why parents are reluctant to immunize their children, it is important to note the reasons they do opt for vaccination. While the main reason parents endorse vaccination is to protect their own children, protecting the community is also a salient rationale. A 2012 review article found that while only 1–6 percent of parents spontaneously name benefits to others as a primary reason to vaccinate, some 30–60 percent agreed with that assessment when asked if it is an important reason to vaccinate.20

In other words, the altruistic motive to vaccinate may be stronger than is widely assumed—an untapped area of research that could yield new approaches to public persuasion.



One of the liveliest workshop discussions focused on the importance of the vaccine conversations that doctors, nurses, pharmacists, and other providers have with parents—both because it is a time when parents can receive accurate information and because it is a chance for providers to gain insight into parents’ vaccine knowledge, attitudes, and beliefs.

Workshop participants discussed the types of research that would help physicians best prepare for this conversation. Is one type of vaccine-hesitant parent more likely to respond to an argument about societal obligations while another type responds most strongly to a discussion of the diseases themselves? Is there any way to identify vaccine-rejecting parents whose minds will never be changed?

Workshop attendees also discussed a finding that has emerged from recently published research: Parents who are told by providers what vaccines their children will get are less likely to resist those recommendations than parents whose providers ask them for their input on vaccines.21



7 Philip J. Smith et al., “Parental Delay or Refusal of Vaccine Doses, Childhood Vaccination Coverage at 24 Months of Age, and the Health Belief Model,” Public Health Reports 126 (supplement 2) (2011): 135–146.

8 Centers for Disease Control and Prevention, “Measles—United States, 2011,” Morbidity and Mortality Weekly Report (MMWR) 61 (15) (April 20, 2012): 253–257,; Centers for Disease Control and Prevention, “Measles Press Conference: 50th Anniversary of Measles Vaccine,” Press Briefing Transcript, December 5, 2013,

9 WHO Regional Office of Europe, Immunization Highlights, 2011–2012 (Copenhagen, Denmark: WHO Regional Office for Europe, December 2, 2011), 9.

10 World Health Organization, “Measles, Fact sheet N°286,” updated February 2014,

11 Centers for Disease Control and Prevention, “Pertussis Outbreak Trends,” updated September 2013,

12 National Institutes of Health, “How To Whip Whooping Cough,” News in Health, June 2013,

13 World Health Organization, “Poliomyelitis in Nigeria and West/Central Africa,” World Health Organization Global Alert and Response, June 18, 2008,

14 Douglas J. Opel et al., “Development of a Survey to Identify Vaccine-Hesitant Parents,” Human Vaccines and Immunotherapeutics 7 (4) (April 2011): 419–425, doi: 10.4161/hv.7.4.14120,

15 Heidi J. Larson, “Negotiating Vaccine Acceptance in an Era of Reluctance,” Human Vaccines and Immunotherapeutics 9 (8) (July 29, 2013): 1779–1781.

16 Daniel J. DeNoon, “WebMD Survey: Safety Biggest Vaccine Worry for Parents,” WebMD, March 31, 2011,

17 Robert Sears, The Vaccine Book (New York: Little, Brown, 2007), 96–97.

18 J. S. Rota et al., “Processes for obtaining non-medical exemptions to state immunization laws,” American Journal of Public Health 91 (2001): 645–648; Heidi J. Larson, “Public Trust in Vaccines: A Global Perspective,” The Vaccine Confidence Project, London School of Hygiene & Tropical Medicine, presented at Public Trust in Vaccines: Defining a Research Agenda, September 26, 2013.

19 Emily K. Brunson, “How Parents Make Decisions about their Children’s Vaccinations,” Vaccine 31 (46) (November 2013): 5466–5470.

20 Maheen Quadri-Sheriff et al., “The Role of Herd Immunity in Parents’ Decision to Vaccinate Children: A Systematic Review,” Pediatrics 130 (3) (September 1, 2012): 522; originally published online August 27, 2012, doi: 10.1542/peds.2012-0140.

21 Douglas J. Opel et al., “The Architecture of Provider-Parent Vaccine Discussions at Health Supervision Visits,” Pediatrics 132 (6) (December 2013): 1037–1046; published November 4, 2013, doi:10.1542/peds.2013-2037.