Vaccine Acceptance: Barriers, Perceived Risks, Benefits, and Irrational Beliefs

1

Introduction

Vaccination is recognized as one of the greatest public health achievements of the last century, likely saving more lives in the last 50 years than any other health intervention. For continued success, however, high population vaccination coverage rates need to be attained and sustained. Immunization not only protects the individual, but also, in many instances, provides community protection against vaccine-preventable diseases through herd immunity. Sadly, reported uptake rates are falling short of national and international targets. An increasing number of parents are choosing to delay and/or refuse some or all vaccines leading to faltering community protection. Clusters of unvaccinated individuals have provided fertile ground for recent major outbreaks of vaccine preventable diseases such as measles, mumps, rubella, poliomyelitis, and pertussis.

For more than a decade, public health experts have been concerned about the growing resistance to immunization. Widespread acceptance of vaccines can no longer be taken for granted. To address this problem of vaccine hesitancy and refusal, a better understanding of the underlying dynamics is fundamental. In 2014, the World Health Organization (WHO) underlined the urgent need for effective interventions to address vaccine hesitancy and increase vaccine acceptance.

The chapter examines the complex interplay among factors that influence vaccine acceptance such as knowledge, risk perception, past experiences, and personal context, as well as the impact of broader sociocultural, historical, and political landscapes that “gives shape to ideas and ideals” about health, prevention and what a good citizen does about vaccination. Of course, access to vaccines and vaccination services—the “supply side”—is a crucial determinant affecting vaccine uptake rates, but the focus here is on the “demand side” of vaccination. Vaccination hesitancy concepts are described, followed by the broader factors influencing vaccine hesitancy and the examination of the drivers of vaccine acceptance, with a special focus on risk perception and risk communication.

2

From vaccine hesitancy to vaccine demand: Making sense of terminology and concepts

“Vaccine acceptance,” “vaccine confidence,” “trust in vaccines,” “vaccine hesitancy,” “anti-vaccinationism,” “vaccine demand”; a plethora of terms and concepts are used—sometimes interchangeably—to describe both individuals decision making about vaccination as well as broader societal support of vaccination programs. A common understanding is important as ambiguities make it difficult to describe, compare, and monitor the different factors implicated in vaccination decisions as well “hampering both research and intervention” work.

The dichotomous perspective on vaccination attitudes and behaviors is no longer tenable. Instead, a spectrum of vaccine beliefs and associated behaviors between complete refusal of all vaccines and full vaccine acceptance must be recognized. People can occupy different (or many) places along this continuum of attitudes and behaviors and this may vary by time context, place and vaccine ( Fig. 26.1 ).

Vaccine hesitancy is a concept now frequently used in discussions of vaccine acceptance. The WHO Strategic Advisory Group of Experts (SAGE) Working Group on Vaccine Hesitancy defined vaccine hesitancy as “delay in acceptance or refusal of vaccines despite availability of vaccine services.” According to this group, the scope of vaccine hesitancy includes instances where “vaccine acceptance in a specific setting is lower than would be expected, given the availability of vaccination services.” A vaccine-hesitant person can delay, be reluctant (but still accept), or refuse one, some or all vaccines. Even people who accept vaccination or have their child vaccinated can still have serious doubts and worries and be considered as vaccine-hesitant. This latter group is an important target for vaccination promotion interventions in order to encourage resiliency as they are “at-risk” of delaying or refusing vaccination. They are more receptive to public health and health-care providers’ messages than outright vaccine refusers.

Vaccine hesitancy has been criticized as being an “ambiguous notion with an uncertain theoretical background.” Nevertheless, it is useful as the term is becoming increasingly used, in the literature and in practice, to encompass this heterogeneous group of individuals with diverse vaccine attitudes and acceptance behaviors. Application of this concept can also be challenging.

The WHO SAGE Working Group on Vaccine Hesitancy recognized that more efforts are needed to improve the ability to describe, measure, and assess vaccine hesitancy at the country and regional levels. Because research has mainly focused on the metrics of vaccine uptake (coverage rates, delays, refusals), the degrees to which vaccine hesitancy influences vaccination behaviors remains an important, but complex, domain for investigation. Validated tools that can identify patterns of vaccine hesitancy in individuals, subgroups, and populations over time, differentiating outright refusers from the hesitant, are much needed. However, because the factors influencing vaccine acceptance and hesitancy not only vary within and between populations and subgroups, but also according to context, time, and vaccine; diverse types of data and measurement approaches are needed to capture, quantify, and describe hesitancy.

The concept of vaccine hesitancy has also been criticized as being negative, misleadingly implying that the number of people strongly opposed to vaccines is on the rise, which could then negatively impact the provaccination social norm. The more commonly used positive alternative for vaccine hesitancy is vaccine confidence. However, the WHO SAGE Working Group on Vaccine Hesitancy’s review of the evidence highlighted that confidence is too narrow, as it is only one of the three major factor groups that can contribute to vaccine hesitancy ( Table 26.1 ).

A further term that needs to be differentiated is vaccine demand and its relationship to hesitancy. The second strategic objective of the Global Vaccine Action Plan (GVAP) states that “individuals and communities understand the value of vaccines and demand immunization as both their right and responsibility.” Nichter has differentiated active demand for vaccinations—adherence by an informed public—from passive acceptance of vaccinations—compliance by a public which yields to recommendations and social pressure and pointed out that “demand is often low, even among populations having impressive immunization rates.” Hence, demand is clearly a step further than just acceptance of vaccines by a population ( Fig. 26.1 ).

3