14PART 1 The Profession of Medicine

crisis of confidence many patients feel toward HCPs and the health care

system. Studies demonstrate that an unambiguous, strong recommendation by trusted HCPs is most often the reason that patients, including those who are vaccine hesitant, choose to vaccinate. Strategies

for counseling vaccine-hesitant and vaccine-resistant patients will be

presented and examples of strong vaccine recommendations provided.

Presenting strategies to increase vaccine demand at a system and policy

level is beyond the scope of this chapter. While some physicians may

have roles that allow them to act at this level, all physicians can act and

influence their individual patients. Strategies to create active vaccine

demand at the individual level alone will not solve vaccine hesitancy,

but vaccine hesitancy cannot be addressed without these efforts. For

further discussion of immunization principles and vaccine use, see

Chap. 123.

■ VACCINE COVERAGE AND OUTBREAKS

The epidemiologic data from measles outbreaks over the past 10 years

provide an interesting illustration of the effects of vaccine opposition

and hesitancy. For further discussion of measles, see Chap. 205.

North America Herd immunity occurs when enough individuals

in a population become immune to an infectious disease, usually

through vaccination, that transmission of the infection stops. The level

of immunity (or level of vaccine coverage) required to confer herd

immunity varies with the specific infectious disease. Because measles is

a highly contagious virus, a coverage rate of 93–95% must be achieved

for vaccination to confer herd immunity and interrupt measles transmission. National coverage estimates place one-dose measles vaccine

coverage rates in 2-year-old children at 92% in the United States and

88% in Canada. In spite of these relatively high levels of coverage in

young children, numerous measles outbreaks have occurred in both

countries since 2010 (Table 3-1).

The vast majority (>80%) of measles cases described in Table 3-1

occurred in under- or completely unvaccinated individuals. Of note,

many of these outbreaks highlight pockets of significantly under- or

unvaccinated individuals that are not apparent in national vaccine coverage statistics. Moreover, many of the outbreaks listed in Table 3-1 were

ignited by unvaccinated returned travelers from areas with existing

TABLE 3-1 Measles Outbreaks in North America

YEAR/PLACE NO. OF CASES REASON

2010/Canada 70 An infected traveler to the 2010 Winter Olympics transmitted infection to an under- and unvaccinated local population

in British Columbia.

2011/Canada 776 Disease was imported from France by an unvaccinated returned traveler to Quebec. The outbreak spread in a

nonvaccinating religious community and outside that community. A majority of cases occurred in under- and

unvaccinated persons.

2011/United States 118 Of 118 cases, 46 were in returned travelers from Europe and Asia/Pacific regions; 105 cases (89%) occurred in

unvaccinated persons.

2013/United States 58 Disease was imported by a returned unvaccinated traveler from Europe. The outbreak spread in a nonvaccinating

religious community in New York.

2014/Canada 433 Disease was imported from the Netherlands. The outbreak spread in a nonvaccinating religious community in British

Columbia.

2014/United States 383 The outbreak occurred in nonvaccinating religious communities in Ohio.

2015/United States 147 A multistate/multicountry outbreak was linked to Disneyland amusement park. More than 80% of cases occurred in

unvaccinated persons.

2015/Canada 159 Disease was imported from the United States (part of the Disneyland outbreak) by an unvaccinated traveler. The

outbreak spread in a nonvaccinating religious community in Quebec.

2017/United States 75 The outbreak occurred in an under-vaccinated community in Minnesota; 95% of patients were unvaccinated.

2018/United States 375 Disease was imported by returned unvaccinated travelers from Israel. The outbreak spread in nonvaccinating religious

communities in New York and New Jersey.

2019/Canada 31 Disease was imported from Vietnam by a returned traveler to British Columbia. The outbreak spread throughout

local area schools in under- and unvaccinated persons and resulted in a province-wide measles mass immunization

campaign for schoolchildren.

2019/United States 1282 Outbreaks occurred in 10 states; 73% of cases (~935) were linked to outbreaks in nonvaccinating religious communities

in New York.

Source: Centers for Disease Control and Prevention and Public Health Agency of Canada.

since Edward Jenner introduced the first vaccine against smallpox in

the eighteenth century. So why did the World Health Organization

rank these attitudes as one of the ten greatest threats to public health in

2019? Are current opposition and hesitancy any different from what has

been seen before? Many sociologists, public health experts, and health

care providers (HCPs) argue yes. Recent social and cultural trends,

combined with new communication formats, have converged to create

a particularly potent form of hesitancy and what some have labeled a

crisis of confidence. This crisis manifests as a lack of trust in specific

vaccines, vaccine programs, researchers, HCPs, the health care system,

pharmaceutical companies, academics, policymakers, governments,

and authority in general. (See “Focus: COVID-19 Vaccine Hesitancy,”

below.)

The roots of modern vaccine hesitancy and opposition—defined as

delay or rejection of vaccines in spite of availability—vary depending

on the place and the population. For some individuals and communities, pseudoscience and false claims about the safety of existing vaccines

(e.g., an unsupported link between measles vaccine and autism) have

driven fears, increased hesitancy, and decreased acceptance. For others,

real safety events, such as the association of narcolepsy with a specific

pandemic influenza vaccine (Pandemrix), have justified concerns. In a

few locations (e.g., Ukraine, Pakistan), vaccine hesitancy is the result

of failed health systems or even state failures. Finally, for some groups,

including some fundamentalist religious groups and alternativeculture communities, vaccine hesitancy and opposition reflect exclusion from and rejection of mainstream society and allopathic health

care and manifest as a deep distrust of these institutions and their

HCPs. Although the genesis of modern vaccine hesitancy is multifactorial, its outcomes are uniform: a decrease in vaccine demand and

uptake, a decrease in coverage by childhood and adult vaccines, and

an increase in vaccine-preventable diseases, outbreaks, and epidemics

of disease. Addressing this crisis and moving people from vaccine

hesitancy and refusal to acceptance and active demand require intervention at multiple levels: the individual, the health system (including

public health), and the state.

This chapter will define vaccine hesitancy and briefly describe its

determinants and effects in North America (the United States and

Canada). Physicians and other HCPs are well positioned to address the

Vaccine Opposition and Hesitancy

15CHAPTER 3

outbreaks or epidemics, who spread disease into an unvaccinated or

under-vaccinated community. Many of the outbreaks were contained

within the nonvaccinating community, but several spread to other

under-vaccinated communities geographically contiguous with the

outbreak community. More concerning still are the cases and outbreaks

originating in communities that had not previously been identified as

nonvaccinating. These cases likely highlight pockets of unvaccinated

individuals who object for cultural rather than religious reasons. In the

past, these nonvaccinating individuals did not exist in large enough

clusters to sustain the spread of measles. Of further concern is the

number of individuals included in outbreak statistics who have had one

or sometimes even two doses of vaccine and who were thought to be

protected but who still end up with the disease. The assumption is that

one or two doses provide full disease immunity, but this is not always

true. Often, individual level characteristics (age, immune compromise,

etc.) affect the individual’s response to the vaccine and their level of

protection. In other instances, vaccine protection can wane over time,

thus leaving fully immunized individuals susceptible to infection. In

fact, when herd immunity breaks (i.e., the level of immunity in a community becomes too low to prevent transmission of disease), the occurrence of cases even in fully immunized persons is seen, as reflected in

outbreak statistics. As a result of decreased vaccination rates and the

resulting disruption of herd immunity, these individuals may become

more identifiable as non-immune.

Outside North America Although overall coverage rates may still

be high in North America, they are lower in other parts of the world. In

Samoa, for example, measles–mumps–rubella (MMR) vaccine coverage

before a recent outbreak was 31%; in the Philippines, it was 67%. Twenty

years ago, vaccine coverage was sufficiently high in some parts of the

world, including Europe, that an unvaccinated traveler from a nonvaccinating community to most regions would have been protected by herd

immunity at their destinations. Today that is not the case: such travelers

are likely to become infected in a country with active measles transmission and return home to spread the infection into their communities

and possibly beyond. Thus active measles transmission, whether at

home or abroad, places individuals who rely on herd immunity (e.g.,

immunocompromised persons and young infants) at increased risk.

■ FACTORS IN VACCINE HESITANCY

Vaccination coverage rates provide an estimate of the proportion of

children or adults in the population who have been vaccinated, but

they do not indicate the proportion of individuals who are vaccine

hesitant. An individual may be fully vaccinated but still be hesitant

about the safety and effectiveness of vaccines, or an individual may

be unvaccinated as a result of access issues but may not be hesitant.

Therefore, in attempts to understand a patient’s lack of vaccination, it is

important to distinguish persons who are hesitant and refuse vaccines

from those who need assistance to access the health care system and

successfully complete vaccination. To this end, an understanding of

vaccine hesitancy and its determinants is needed.

Vaccine hesitancy and opposition are defined by the World Health

Organization’s SAGE Working Group on Vaccine Hesitancy as a “delay

in acceptance or refusal of vaccines despite availability of vaccination

services.” The SAGE group describes vaccine hesitancy as “complex

and context specific, varying across time, place, and vaccines.”

It is useful to frame vaccine acceptance as a continuum pyramid,

with active demand for all vaccines representing the largest group at

the bottom of the pyramid and outright refusal of all vaccines depicted

in the smallest group at the top. In the middle lies vaccine hesitancy,

in which the degree of vaccine demand and acceptance varies. Fortunately, for disease control efforts, most individuals fall within the

active-demand category or, if they are hesitant, still accept all vaccines.

Hesitancy can be influenced by complacency, convenience, and confidence (Fig. 3-1).

Complacency is self-satisfaction when accompanied by a lack of

awareness for real dangers or deficiencies. Complacency exists in

communities and individuals when the perceived risks of vaccinepreventable diseases are low and vaccination is not deemed a necessary

preventive action. This attitude can apply to vaccination in general or

to specific vaccines, such as influenza vaccines. Actual or perceived

vaccine efficacy and effectiveness contribute to complacency. Patients

who are complacent about vaccine-preventable diseases prioritize

other lifestyle or health factors over vaccination. These individuals can

be influenced toward vaccination by a strong recommendation from

a trusted HCP or a local influenza outbreak. They can be influenced

away from vaccination by a vaccine scare or misinformation on social

• Strong distrust of health system/pharmaceutical industry/government

• Strong-willed and committed against vaccines

• Negative or traumatic experiences with HCPs and health system

• May use natural approach to health/alternative HCPs

• May have strong religious/moral considerations for refusal

• May cluster in communities (geographic and online)

• Vaccination is very unlikely; alternative strategies to protect individual and community must be discussed.

Refuses

• Questions safety and necessity of vaccines

• Actively seeks information from many sources

• Has conflicting feelings on whom to trust

• Social norm is not vaccinating.

• May have had negative or traumatic experience with health system

• Vaccination may not occur; a strong trust relationship with HCP and many visits and conversations are

 required.

Late and

selective

• Focused on vaccine risks

• Conversation with trusted HCP strongly influential

• Trusts HCPs

• Actively seeking information and wants to verify it

• Wants advice specific for their child

• Confused by conflicting information

• Social norm is vaccinating, but individual may feel conflicted by this norm.

• Vaccination requires longer conversation and may require multiple visits.

• Focused toward vaccine risk

• Complacency: low perceived benefits of vaccination

• Can move up or down continuum as a result of various influences (HCP

 recommendation, vaccine scare, outbreak)

• Trusts HCPs and health system

• Convenience: need few barriers to vaccination

• Vaccination requires longer conversation but likely can be performed at same

 visit; potential exists to move to active demand.

Hesitant – minor doubts

and concerns

• Confidence

• Considers vaccines important

• Considers vaccines safe

• Trusts HCP/vaccines/health system

• Social norm is vaccinating

• Very short conversation with HCP about vaccination, in which HCP

 should address any questions to maintain active-demand status

Active demand – no doubts or

concerns

Accepts

vaccines

Rejects

vaccines

Characteristics

Presumptive

Communication

Approach

Hesitant – many

doubts and

concerns

Participatory

Communication

Approach

FIGURE 3-1 Vaccine acceptance continuum. HCPs, health care providers. (Adapted from J Leask et al: BMC Pediatrics 12:154, 2012; AL Benin et al: Pediatrics 117:1532, 2006;

and E Dubé, NE MacDonald: The Vaccine Book, 2016, pp. 507-528.)

16PART 1 The Profession of Medicine

media. Finally, the real or perceived ability of patients to take the action

required for vaccination (i.e., self-efficacy) influences the role complacency plays in hesitancy and willingness to seek vaccination.

Convenience is determined by the degree to which conversations

about vaccination and other services can be provided in culturally

safe contexts that are convenient and comfortable for the individual.

Clearly, convenience varies by community, health clinic, and even

patient. Persons who are criticized or scolded for not vaccinating

themselves or their children may not feel comfortable or safe accessing

health services. Factors such as affordability, geographic accessibility,

language, and health literacy are important considerations when evaluating the convenience of existing clinical care. Any of these factors

can affect vaccine acceptance and can push a patient who has some

hesitancy toward vaccinating or not vaccinating.

Confidence is based on trust in the safety and efficacy of vaccines,

in the health care system that delivers vaccines (including HCPs), and

in the policymakers or governments who decide which vaccines are

needed and used. A continual erosion of confidence around vaccination, health systems, and governments drives today’s hesitancy and

has been amplified by larger social and cultural trends in medicine,

parenting, and information availability.

■ SOCIAL AND CULTURAL TRENDS

Individualized Health Care Over the past 30 years, the focus of

medicine and health care has shifted to patient-oriented, individualized care, with an increasing emphasis on treatment and prevention

options tailored to the individual patient. In vaccination programs,

this shift has manifested as requests for individualized vaccine recommendations and customized immunization schedules. The increasing

personalization of medicine, while positive overall, has forced public

health away from a focus on the community and its common good and

has created tension between individual rights and community health.

Parenting Trends The desire for an individualized approach to

medicine and vaccination reflects broader cultural trends concerning

individual risk management: accordingly, the individual is to blame

for bad outcomes, and public institutions cannot be trusted to manage

technological (i.e., vaccine-related) risks. This viewpoint is directly

linked with cultural shifts in parenting and social norms defining

what it means to be a “good parent.” The image of a good parent has

been reframed to refer to someone whom several investigators have

described as “a critical consumer of health services and products,

accounting for their own individual situation as they see it with little

regard for the implications of their decision on other children.” The

archetypical good parent no longer unquestioningly trusts HCPs and

other authorities and experts. According to this social norm, “good

parents” should seek individual medical advice that is tailored for their

child and specific to that child’s needs. While in essence not a bad

thing, this norm can conflict directly with public health vaccine recommendations and schedules that are organized to maximize community health and to facilitate efficient provision of care at a community

level.

Traditional Media Newspapers, radio, and television have been

criticized for their coverage of vaccines and in particular their coverage

of the alleged link between MMR vaccine and autism. By offering equal

coverage throughout the early to mid-2000s for both the scientific

evidence and unproven claims of MMR vaccine harms, traditional

media outlets provided a forum and a megaphone for the spread of

pseudoscience. Equal coverage leads to false equivalencies. Celebrity

advocates further amplified the message via this channel. The boost

that traditional media provided to active vaccine resistance and, less

directly, to vaccine hesitancy has not been adequately measured but

must be considered in any discussion of vaccine hesitancy. After

headlines about multiple outbreaks of measles and other vaccinepreventable diseases and continued direct criticism of the equalcoverage approach, some traditional media now reject and attempt to

discredit pseudoscience. The effect this stance will have on increasing

vaccine confidence is unknown.

The Internet and Social Media Approximately 90% of Americans

and 91% of Canadians use the Internet, and 80% of Americans and

60% of Canadians have a social network profile. Widespread access

to social media can be empowering, but it is also problematic. The

Internet and social media require users to select their information

sources, creating an environment described as an “echo chamber” in

which individuals choose information sources harboring beliefs or

opinions similar to their own and thereby reinforcing their existing

views. This situation has created a new platform for further spread of

vaccine misinformation (inaccuracies due to error) and disinformation

(deliberate lies) and has provided a forum for vaccine-resistant individuals, including celebrities, to organize and raise funds to support their

efforts. The harmful effects of Internet and social media use on vaccine

hesitancy have been well documented. Vaccine hesitancy increases for

parents who seek their information from the Internet. Unfortunately,

public health and health care institutions have been slow to adapt to

this new communication medium and to recognize its influence and

impact. In this medium, personal stories and anecdotes are now viewed

as data and disproportionately influence vaccine decision-making,

while traditional, more authoritative, fact-based information sources

are deemphasized. Centralized monitoring by jurisdiction of vaccine

misinformation and disinformation, with summaries of the relevant

discourses and rebuttals provided to HCPs, has been proposed as a

potential way to counter the influence of social media on vaccine hesitancy. While such strategies have been applied in single jurisdictions

and appear to have had some success, their applicability to a broader

context is unknown. Moreover, the resources for such a coordinated

response have not been made available, and individual HCPs have been

left to counter popular, shifting, viral communications on their own,

patient by patient.

As with traditional media, the social media landscape appears to

be shifting. In 2019, the proliferation of anti-vaccination information

combined with measles outbreaks in North America and increasing

pressure from health leaders led large social media companies (Facebook, Instagram, Pinterest) to deemphasize anti-vaccination information by removing relevant advertisements and recommendations and

decreasing their prominence in search results. While it is too soon to

determine the effects of these measures, critics are skeptical that they

will have the intended result of reducing vaccine misinformation and

disinformation. Early evidence shows that misleading content is still

widely available, with anti-vaccine advertisements now using the term

“vaccine choice” to avoid censorship. More disturbingly, public health

advertisements in support of vaccination have been included in social

bans and removed from social media sites.

In a more grassroots effort, providers and vaccine supporters have

united on social media to provide online support and evidence-based

facts to providers and others who support vaccines when they are

attacked digitally by anti-vaccine supporters. For example, Shots Heard

Round the World (www.shotsheard.com) is an effort led by two U.S.

pediatricians to provide advice and support for HCPs who speak out

about the importance of vaccines. Such efforts harness the power of

social media in ways similar to those used by vaccine opponents and

may prove successful in combating vaccine hesitancy.

Given these social and cultural trends, no one should be surprised

when individuals now question vaccination, express confusion about

conflicting information and information sources, and feel unsure

whom to trust. Their broader social context is telling them they should

question everything and trust no one. This message is reinforced via

misinformation and disinformation on social media. Recent vaccinepreventable disease outbreaks illustrate that effective engagement

with individuals cannot be accomplished through one-way, top-down

information provision (which still is often the de facto choice for health

system communication), but rather requires a dialogue that takes into

account the social processes surrounding individual vaccination decisions. It is at the interface between the individual and the health system

in which conversations between HCPs and their patients can have the

greatest impact. It is critical for all HCPs to discuss vaccines and provide strong vaccine recommendations—including HCPs who do not

administer vaccines but who have established trust with their patients.