ReviewUnderstanding vaccine hesitancy around vaccines and vaccination from a global perspective: A systematic review of published literature, 2007–2012
Introduction
Vaccination is often cited as one of the most important achievements of public health. However, this success has always been challenged by individuals and groups who question, and sometimes refuse, vaccines for a variety of reasons including religious, scientific and political [1], [2], [3]. Present day debates around vaccination are increasingly complex, as more vaccines and combinations of vaccines have become available and modes of global communication have become far more ubiquitous, fast and non-hierarchical. Rapid global sharing of public concerns and sometimes uncertainty around vaccines [4] are leading to an increase in the number of people questioning vaccines, seeking alternative vaccination schedules [5], [6] and sometimes delaying or refusing vaccination [7].
In recent years, there has been growing attention to what has been termed “vaccine hesitancy” [8], [9], [10], de-polarizing earlier attention to “pro”- versus “anti”-vaccination individuals and groups. Vaccine-hesitant individuals have been defined as a heterogeneous group in the middle of a continuum ranging from total acceptors to complete refusers. These “hesitant” individuals may refuse some vaccines, but agree to others, delay vaccines, or accept vaccines but are unsure of doing so [11], [12].
The behaviour of vaccine-hesitant individuals or communities is complex, and determinants of hesitancy are highly variable. In Greece [13], socioeconomic factors, such as number of other siblings and father's education, were the most important predictive factors of both under- and delayed childhood vaccination, and parental attitudes and beliefs about vaccination were found to be non-significant in this regard. A study in Nigeria found that partial immunization was most influenced by factors such as maternal availability, and lack of knowledge, whereas parental disapproval played a more influential role on non-immunization [14]. Another study, on MMR vaccine in the UK, found that different factors influenced decision-making at each dose, with degrees of influence also varying at each dose [15]. While several systematic reviews have investigated factors that influence vaccine hesitancy across different populations and vaccines [16], [17], [18], [19], there is evidence to suggest that not all potentially relevant factors have been identified or thoroughly investigated [15], [20].
Recognizing that vaccine hesitancy is an important issue, and given its potential to impact on vaccine coverage, the Strategic Advisory Group of Experts [SAGE] on Immunization established a Working Group dealing with vaccine hesitancy in March 2012 [21]. In line with its assigned terms of reference, the SAGE working group first defined “vaccine hesitancy” as:
A behaviour, influenced by a number of factors including issues of confidence [do not trust vaccine or provider], complacency [do not perceive a need for a vaccine, do not value the vaccine], and convenience [access]. Vaccine-hesitant individuals are a heterogeneous group who hold varying degrees of indecision about specific vaccines or vaccination in general. Vaccine-hesitant individuals may accept all vaccines but remain concerned about vaccines, some may refuse or delay some vaccines, but accept others; some individuals may refuse all vaccines.
Building on the above definition, the working group also drafted a “Model of determinants of vaccine hesitancy” (Fig. 1) organized around three key domains: 1. Contextual influences – including historic, socio-cultural, environmental, health system/institutional, economic or political factors; 2. Individual and group influences – including influences arising from personal perception of the vaccine or influences of the social/peer environment; and, 3. Vaccine and vaccination-specific issues which are directly related to the characteristics of the vaccine or the vaccination process (Fig. 1). This model includes a broad selection of factors that have been identified as potential influencers of vaccine hesitancy drawn from the collective experience and insights of the SAGE WG members, all of whom are considered experts in their field, and represent diverse disciplines.
With reference to the above definition and model, the specific objectives of this systematic review were to:
- 1)
Identify research on vaccine hesitancy and related terms globally;
- 2)
Gain an appreciation of vaccine hesitancy in different settings including its context-specific causes, its expression and its impact; [this was approached by identifying factors that act as either barriers or promoters of vaccination]; and
- 3)
Inform the further development of the SAGE model mapping determinants of vaccine hesitancy.
The SAGE WG asked to focus this systematic review on childhood vaccination. Childhood vaccinations are generally scheduled to be received from 0-to-six years of age. As this review was focused on instances of non-conformity to this schedule, the age range for the childhood category was kept flexible. Across the studies included in this review, the oldest child participant was 7 years old, and the cut-off age was therefore set as such.
Section snippets
Search strategy and selection criteria
A search strategy was developed in Medline and then adapted as required by differential indexing across several multidisciplinary mainstream and regional databases including: Medline, Embase Classic & Embase, PsychInfo, Cochrane, CINAHL Plus, Web of Science, IBSS, LILACS, AfricaWideInfo and IMEMR. The strategy included an extensive list of keywords (Table 1) and related MeSH/subject headings in an effort to capture the many dimensions and expressions of vaccine confidence, trust and hesitancy.
Identified literature
31,379 records (all languages) were identified from the databases using the combined searches (Fig. 2). After the removal of duplicates, 16,010 records were shortlisted for screening by title and abstract, of which 1187 were included for full-text assessment. Thirty-three articles were not available in full text and an additional ten articles were added from the SAGE Working Group members, which summed to a total of 1164 articles to be analyzed. All of these articles were included in the
Discussion
Peer-reviewed studies on vaccine hesitancy were found across all regions. The majority of studies were conducted in the EUR and AMERICAS regions, which alone have seen a two-fold increase in research on this topic during the period 2007–2012. While this finding might suggest a greater prevalence of vaccine hesitancy and related issues in these regions, the dearth of research available in other regions, where the majority of the world's population lives, makes conclusive statements difficult.
A
Conclusion
Vaccine hesitancy has emerged as an important concept in understanding the scope of vaccine acceptance behaviours. The development of the SAGE Working Group model of determinants of vaccine hesitancy is a meaningful step towards evolving a set of indicators to effectively monitor the evolution of vaccine hesitancy, in order to engage early in vaccine decision-making processes.
However, our findings clearly show that additional sources of information must be tapped to ensure that the model is
Acknowledgements
The authors acknowledge the contribution of the members of the SAGE Working group on dealing with vaccine hesitancy in the development of the model (Fig. 1) and in feedback on the early drafts of the article.
Conflict of interest statement: The research group receives funding from The Bill & Melinda Gates Foundation, Novartis and WHO.
Author contributions: HL and CJ co-lead the review. EE and PP contributed to the review of papers as well as the analysis. DS contributed to the statistical
References (80)
- et al.
Addressing the vaccine confidence gap
Lancet
(2011) - et al.
Parental hesitation as a factor in delayed childhood immunization
J Pediatr Health Care
(2009) - et al.
Socioeconomic factors play a more important role in childhood vaccination coverage than parental perceptions: a cross-sectional study in Greece
Vaccine
(2010) - et al.
Reasons related to non-vaccination and under-vaccination of children in low and middle income countries: findings from a systematic review of the published literature 1999–2009
Vaccine
(2011) - et al.
Factors influencing pandemic influenza vaccination of healthcare workers—a systematic review
Vaccine
(2012) - et al.
Systematically reviewing qualitative studies complements survey design: an exploratory study of barriers to paediatric immunizations
J Clin Epidemiol
(2005) - et al.
Validity and reliability of a survey to identify vaccine-hesitant parents
Vaccine
(2011) - et al.
Linkages between maternal education and childhood immunization in India
Soc Sci Med
(2012) - et al.
Knowledge, attitudes and practices of caregivers regarding Japanese encephalitis in Shaanxi Province, China
Public Health
(2011) - et al.
Risk factors of underutilization of childhood immunizations in ultraorthodox Jewish communities in Israel despite high access to health care services
Vaccine
(2012)
Maternal knowledge, attitudes and beliefs regarding gastroenteritis and rotavirus vaccine before implementing vaccination program: Which key messages in light of a new immunization program?
Vaccine
Homeschooling parents’ practices and beliefs about childhood immunizations
Vaccine
Attitudes of nurses toward current and proposed vaccines for public programs: A questionnaire survey
Int J Nurs Stud
New vaccines offering a larger spectrum of protection against acute otitis media: Will parents be willing to have their children immunized?
Int J Pediatr Otorhinolaryngol
Psychosocial determinants of parents’ intention to vaccinate their newborn child against hepatitis B
Vaccine
Interpretation of primary care physicians’ attitude regarding rotavirus immunization using diffusion of innovation theories
Vaccine
Barriers to implementation of the new targeted BCG vaccination in France: a cross sectional study
Vaccine
Canadian paediatricians’ opinions on rotavirus vaccination
Vaccine
Determining immunization coverage rates in primary health care practices: a simple goal but a complex task
Int J Med Inf
Misperceptions regarding influenza vaccine safety for individuals with chronic medical illness
Prev Med
Timing of children's vaccinations in 45 low-income and middle-income countries: an analysis of survey data
The Lancet
Timing of children's vaccinations in 45 low-income and middle-income countries: an analysis of survey data
Lancet [British edition]
Parental education and child health-understanding the pathways of impact in Pakistan
World Dev
Education and debate, anti-vaccinationists past and present
BMJ
‘They might as well brand us’: working-class resistance to compulsory vaccination in Victorian England
Social History of Medicine
The politics of prevention: ANTI-vaccinationism and public health in nineteenth-century England
Med Hist
Alternative vaccination schedule preferences among parents of young children
Pediatrics
Frequency of alternative immunization schedule use in a metropolitan area
Pediatrics
Parents with doubts about vaccines: which vaccines and reasons why
Pediatrics
Development of a survey to identify vaccine-hesitant parents: the parent attitudes about childhood vaccines survey
Hum Vaccin
H1N1 and influenza viruses: why pregnant women might be hesitant to be vaccinated
Canadian Family Physician
Development of a survey to identify vaccine-hesitant parents: The parent attitudes about childhood vaccines survey
Human Vaccines
Qualitative analysis of mothers’ decision-making about vaccines for infants: the importance of trust
Pediatrics
Maternal reasons for non-immunization and partial immunization in northern Nigeria
J Paediatr Child Health
Attitudinal and demographic predictors of measles-mumps-rubella vaccine [MMR] uptake during the UK catch-up campaign 2008-09: cross-sectional survey
PLoS ONE
Factors associated with suboptimal compliance to vaccinations in children in developed countries: a systematic review
Curr Med Res Opin
Parental knowledge, attitudes, and behaviours towards human papillomavirus vaccination for their children: a systematic review from 2001 to 2011
Obstet Gynecol Int
How to communicate with vaccine-hesitant parents
Pediatrics
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