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Unpacking the Root Causes and Consequences of Vaccine Hesitancy


This is part 2 of a 3-part vaccine series covering the potential of vaccines for infectious diseases, the impact of the antivaccination movement, and the promise of vaccines for cancer treatment.

Read part 1

The headlines are hard to ignore: the number of measles cases are nearing a new high since the disease was thought to have been eliminated in 2000. In the first 3 months of 2019, there were more cases of the measles than in all of 2018, and as of April 19, 626 cases of the measles have been confirmed in 22 states. Mumps outbreaks, albeit less prevalent, have also occurred, most notably at Temple University.

A piece in STAT made the rounds in March, as it detailed the experience of a 6-year-old boy who had never been vaccinated and got a cut on his forehead in 2017. The boy got tetanus, marking Oregon’s first pediatric case of tetanus in more than 30 years. After a weeks-long stay at the hospital, which came with a bill of more than $800,000, his parents still refused to allow doctors to give their son vaccinations for measles and other disease.

Stories like these have continued to make headlines over the last year, highlighting a prominent, global issue: vaccine hesitancy.

In January, vaccine hesitancy was named 1 of the top 10 threats to global health by the World Health Organization (WHO). According to WHO, addressing vaccine hesitancy requires not just an understanding of the magnitude of the problem, but also a diagnosis of the root causes, tailored evidence-based approaches to addressing hesitancy, and monitoring and evaluating the interventions.

To understand vaccine hesitancy, it’s also crucial to note that no single intervention will address the issue because there can be multiple interrelated determinants underlying vaccine hesitancy.

“It’s important to remember when looking at the general public that among those who are vaccine hesitant, many of them are hesitant for different reasons,” explained Amesh A. Adalja, MD, FIDSA, FACP, FACEP, senior scholar, Johns Hopkins Center for Health Security, in an interview with The American Journal of Managed Care®. “It’s not as monolithic as it’s portrayed. You have to look at each case individually.”

Understanding Vaccine Hesitancy and Its Origins

Vaccine hesitancy’s origins date back to the invention of vaccines when the small pox vaccine was created in 1796, explained Adalja. But while vaccine hesitancy is nothing new, it has taken on a more voracious form in recent years.

Adalja credits the start of the modern antivaccine movement to the 1982 film "Vaccine Roulette," which falsely linked the diphtheria, pertussis, and tetanus vaccine to neurologic disorders. This alleged link was later debunked, and the neurologic disorders were proven to be caused by a genetic defect. “But this really galvanized certain parents who were worried about vaccines and who then made themselves into a social pressure group,” explained Adalja.

This movement further gained steam in 1998 when the well-known, now retracted, study published in The Lancet1 by Andrew Wakefield and his colleagues, which suggested the measles, mumps, and rubella (MMR) vaccine may cause autism in children. Despite the small sample size, the uncontrolled design, and the speculative conclusions,1 the paper yielded a strong response, with MMR vaccination rates dropping due to parents’ concern about the risk of autism following vaccination.

The study has since been debunked multiple times, most recently by a study published in the Annals of Internal Medicine—one of the largest studies to date about the issue—that affirmed that there is no connection between the MMR vaccine and autism, even in subgroups of children that some of those opposed to vaccines have claimed might be more vulnerable to the perceived effects.

However, despite the evidence, vaccine hesitancy stemming from both the documentary and the study have persisted. This hesitancy has been exacerbated even further by celebrities like Jenny McCarthy, Jim Carrey, and Robert F. Kennedy Jr, who have been vocal about their antivaccine beliefs.

Social Media

With technology and social media booming over the last decade, these platforms have become a go-to outlet for vaccine hesitant individuals to dispel misinformation about vaccines through avenues like private Facebook groups and Pinterest boards.

“It’s unfortunate that people are using this great technology of social media to spread an anti-technology message,” said Adalja.

In March, 18-year-old Ethan Lindenberger appeared before a Senate committee to discuss his decision to get vaccinated despite the wishes of his mother, who is antivaccine. Lindenberger had grown up without common vaccinations, such as the MMR or chicken pox vaccine, before getting vaccinations starting in December 2018. Lindenberger credited his mother’s antivaccine beliefs to “deeply rooted misinformation” online from organized groups that spread disinformation and “instill fear into the public for their own gain, selfishly.”

Later that month, the American Medical Association (AMA) sent a letter for the chief executive officers of Amazon, Facebook, Google, Pinterest, Twitter, and YouTube urging them to ensure their users have access to accurate, timely, and scientifically-sound information on vaccines.

Recognizing the role they play in stopping the spread of misinformation, some platforms have already taken measures to try and contain this information. Pinterest has blocked all searches for vaccines, which falls under the company’s health misinformation guideline implemented in 2017.

Facebook said in March that it will no longer be recommending groups and pages that spread misinformation and hoaxes about vaccines, will reject ads that include misinformation, and won’t show or recommend content that contains misinformation on Instagram or hashtag pages.

The Role of States

While every state has legislation requiring specified vaccines for students, almost all states grant religious exemptions 17 allow philosophical exemptions for those who oppose vaccinations because of personal, moral, or other beliefs.

In response to recent outbreaks, some states have initiated efforts to remove religious and philosophical exemptions. The Maine House this week approved a bill that removes these exemptions for public school vaccination requirements, and last week, the Washington Senate passed a bill removing personal exemptions for the MMR vaccine.

States that have housed some of this year’s outbreaks have also put forward measures to contain these outbreaks. Public health officials declared public health emergencies in Clark County, Washington, and in certain zip codes in Williamsburg, Brooklyn.

“The goal here is to send a message that people need to act immediately to get vaccinated, and that vaccination is available readily here in the neighborhood and throughout the city,” said New York City Mayor Bill de Blasio as he announced the declaration. As part of the declaration, unvaccinated individuals who live in the named zip codes are required to receive the MMR vaccine. If they do not get vaccinated, they could face a $1000 fine.

According to Adalja, eliminating these exemptions for school-required vaccinations is a move in the right direction. “There’s so many things you can’t bring to school. You can’t bring peanut butter to school, but you can bring measles to school or chicken pox,” he said.

The Role of Healthcare Stakeholders

In addition to the AMA urging media platforms to contain the dissemination of misinformation about vaccines, the association also urged healthcare professionals to encourage vaccination, stating that “parent and patient education provided by physicians is an important factor in influencing higher vaccination rates.”

Public health officials, including Surgeon General Jerome Adams, MD, MPH, have been vocal about the importance of getting vaccinated. In an opinion piece in The New York Times, Adams; CDC Director Robert Redfield, MD; and Brett P. Giroir, MD, assistant secretary for health at HHS, underscored the importance of vaccines, writing, “For those of us who have treated critically ill children with vaccine-preventable diseases, we know firsthand the devastation to the child—and to the family and community—of a death, limb amputation, or severe brain damage that could have been avoided by a simple vaccination.”


1. Wakefield AJ, Murch SH, Anthony A, et al. Ileal-lymphoid-nodular hyperplasia, non-specific colitis, and pervasive developmental disorder in children [published online February 28, 1998]. Lancet. doi: 10.1016/S0140-6736(97)11096-0.

2. Rao TS, Andrade C. The MMR vaccine and autism: sensation, refutation, retraction, and fraud [published online April 2011]. Indian J Psychiatry. doi: 10.4103/0019-5545.82529.

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