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Health Promotion Perspectives. 13(1):21-35. doi: 10.34172/hpp.2023.03

Systematic Review

COVID-19 vaccine hesitancy: A Systematic review of cognitive determinants

Sara Pourrazavi 1, 2ORCID logo, Zahra Fathifar 3, Manoj Sharma 4, 5ORCID logo, Hamid Allahverdipour 1, 2, *ORCID logo
1Research Center of Psychiatry and Behavioral Sciences, Tabriz University of Medical Sciences, Tabriz, Iran
2Health Education & Promotion Department, Tabriz University of Medical Sciences, Tabriz, Iran
3Department of Library, Tabriz University of Medical Sciences, Tabriz, Iran
4Department of Social and Behavioral Health, University of Nevada, Las Vegas (UNLV), Las Vegas, NV 89119, USA
5Department of Internal Medicine, Kirk Kerkorian School of Medicine at UNLV, Las Vegas, NV 89154, USA
*Corresponding Author: Hamid Allahverdipour, Email: allahverdipourh@tbzmed.ac.ir

Abstract

Background: Although mass vaccination is considered one of the most effective public health strategies during the pandemic, in the COVID-19 era, many people considered vaccines unnecessary and, or doubted the effectiveness of the COVID-19 vaccine. This review aimed to tabulate cognitive causes of COVID-19 vaccination hesitancy, which may help public health policymakers overcome the barriers to mass vaccinations in future pandemics.

Methods: For this systematic review, studies pertaining to COVID-19 vaccine hesitancy published up to June 2022 were retrieved from six online databases (Cochrane Library, Google Scholar Medline through PubMed, Scopus, and Web of Science). Inclusion criteria were the studies conducted on people who had a delay in accepting or refusing COVID-19 vaccines, reported the impact of cognitive determinants on vaccine hesitancy, and were written in English in the timeframe of 2020–2022.

Results: This systematic review initially reviewed 1171 records. From these 91 articles met the inclusion criteria. The vaccination hesitation rate was 29.72% on average. This systematic review identified several cognitive determinants influencing vaccination hesitancy. Lack of confidence and complacency were the most frequent factors that predicted vaccine hesitancy.

Conclusion: The identified prevailing cognitive determinants for COVID-19 vaccine hesitancy indicated that using initiative and effective communication strategies would be a determinant factor in building people’s trust in vaccines during the pandemic and mass vaccinations.

Keywords: COVID-19 vaccines, Vaccination hesitancy, Cognitive psychology, Systematic review

Copyright

© 2023 The Author(s).
This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Introduction

The outbreak of the COVID-19 disease caused an emergency situation worldwide by affecting various aspects of human life. Although preventive measures, such as social distancing, wearing face masks in public, being under lockdowns, and quarantines helped to control COVID-19 virus transmission, returning to normal life urgently needed long-term solutions such as universal vaccination.1 COVID-19 vaccine reduced the mortality rate of disease and consequently had many benefits on the health and socio-economic aspects of life in the COVID-19 era.2 Additionally, the vaccines against the coronavirus changed the course of the pandemic to a better status by reducing the severity of COVID-19 disease and the incidence of new cases, even among unvaccinated people, through herd immunity.2 However, the COVID-19 vaccine, like all other new vaccines, faces the age-old public acceptance problem.3 Therefore, not only discovering and making available the COVID-19 vaccine is one of the critical challenges for the policymakers, but it will also be essential to encourage people to get it.4

Even though the effectiveness and safety of many vaccines, such as COVID-19, have been well established, many people consider vaccines unnecessary and doubt their effectiveness and safety.2 Vaccine hesitancy is defined as a postponement in acceptance or denial despite the availability of a vaccine.5 It has been declared one of the top 10 warnings to attaining health for all by the World Health Organization (WHO).2

Vaccine hesitancy has existed since the advent of the vaccines for influenza, human papillomavirus, polio, measles, etc.3 Recently, the world has witnessed people’s hesitation to receive the COVID-19 vaccine.6 COVID-19 vaccine hesitancy threatened doubtful people and the entire society by delaying the threshold of vaccine uptake necessary to achieve herd immunity.2 The acceptance rate of the COVID-19 vaccine in different countries varied from the lowest of 23.6% in Kuwait to 97% in Ecuador.6 In contrast, for successful control of COVID-19, the vaccine hesitancy should not be more than 25%-30%.7

Many reasons can cause doubts about the COVID-19 vaccination, including fear of probable side effects, concern about the rapid vaccine production process, fear of inefficiency, unpleasant effect on some specific diseases,5 lack of trust in clinical trials, the sufficiency of the immune system to fight against COVID-19,2 the spread of fake information and news,7 religious beliefs,8 and political ideology.9 Therefore, the hesitancy of COVID-19 vaccination is not an individual problem; rather, it is a complex, multifaceted behavior that can have different cognitive, behavioral, social, and even political reasons in different societies and times. Although recent literature has investigated its reasons from different perspectives, little cumulative evidence has attempted to summarize in-depth and systematically the cognitive causes of COVID-19 Vaccine hesitancy. Therefore, the purpose of this study was to review the cognitive determinants of hesitancy toward COVID-19 vaccine.


Materials and Methods

Study design and search strategy

Six online databases (viz., Cochrane Library, Google Scholar Medline through PubMed, Scopus, and Web of Science) were searched thoroughly using a methodical approach in accordance with the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) guidelines to identify relevant studies.10 We utilized the study’s research question to drive the search terms, namely, “what cognitive determinants influence COVID-19 vaccine hesitancy?” Therefore, the selected keywords were structured with Boolean operators. An example of this search strategy applied to the PubMed database is available in Supplementary file 1. After removing duplicates, the screening phase generated 723 articles. Moreover, we examined the references of identified publications for relevant studies.

Study selection

Eligibility criteria were established beforehand using the PICO (population, intervention, comparison, and outcomes) design, and the research team (SP, ZF, HA) examined and approved the content validity:

Populations. Articles that included people who had delayed acceptance or refusal of COVID-19 vaccines despite its availability. No additional restrictions on population are considered.

Comparison. No criteria for comparison were applicable.

Outcomes. Any reported impact of cognitive determinants on vaccine hesitancy.

Time. All peer-reviewed journal articles published between January 2020 and June 2022 were included.

Setting. No limitations on the type of settings were imposed.

English language quantitative (cross-sectional studies, randomized controlled trials, non-randomized studies, pre-post studies, and time series) or mixed methods (focused on the quantitative strand) research were eligible study designs. Systematic reviews were excluded but were employed to identify additional eligible studies.

The search strategy was conducted in accordance with the Peer Review of Electronic Search Strategies statement.11 To ensure whether studies met the inclusion criteria, two authors conducted separate searches, screen the titles and abstracts, and then assessing the remaining 106 publications’ full texts.

Screening the full-text and synthesis

For evaluation studies, information extracted included details about study characteristics, participants, setting, the prevalence of hesitation, and the findings related to the outcomes of interest.

Two research team members, SP and ZF, independently pilot-tested the data extraction form utilizing two of the 106 articles and compared and discussed the findings. The feedback was used to refine the form. The final draft of the form was used by SP to extract data from the remaining 104 articles, which were independently checked by ZF. Title and abstract screening, along with full-text screening and cross-validation, were conducted by two review authors (SP and ZF) independently based on the abovementioned inclusion criteria. Any disagreements over a particular study were resolved through mutual discussion with a third reviewer (HA). Subsequently, 18 of the 106 articles were removed, resulting in a final included sample of 88 studies. Studies were excluded if they did not evaluate hesitancy toward COVID-19 vaccine and just measured vaccine acceptance. In addition, those studies which have not pointed out the role of cognitive determinants in hesitancy to the COVID-19 vaccine were eliminated.

We added three additional articles to our enumeration by reviewing the references from the articles. depicts the selection process over four-rounds. Using the PRISMA flow diagram, the documentation and summarization of the identification, screening, eligibility, and selection processes was done. Finally, at total of 91 articles were independently reviewed by SP and ZF. After that relevant data were extracted, and if there were any discrepancies, they were resolved for 100% agreement.

hpp-13-21-g001
Figure 1. The diagram of the study based on PRISMA checklist

Quality assessment

Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) statement was used to conduct qualitative assessment independently with the help of two reviewers (SP and ZF).12 This checklist incorporates 22 criteria. If a study meets a condition, it receives one point, or zero if it is not or only partially disclosed. In this rating a higher overall score means that there is less of methodological bias. We divided each study’s risk of bias score by 22 (the highest possible score) and then multiplied it by 100 to assess the proportional percentage of fulfilled criteria. Any dissenting issues between the reviewers were resolved through discussion and consensus with the help of a third reviewer (HA). Studies’ quality were then sorted into excellent (matching ≥ 85% criteria), good (matching 70 to < 85% criteria), fair (matching 50 to < 70% criteria), and poor (matching < 50% criteria).13


Results

Descriptive findings

This review considered 91 peer-reviewed publications. The investigation comprised COVID-19 vaccine hesitancy studies from 36 different countries. Most surveys were conducted in the United States (n = 15), followed by China and Italy (n = 8 for each country), and Bangladesh (n = 7). Numerous studies were carried out in more than one country.14-18 The study carried out among US households3 had the largest sample size (n = 459 235), while one study carried out among homeless people in the US had the smallest sample size (n = 90).19 Out of these 91 studies, 27 were conducted with the general population, 27 with adults, 11 with health care workers, 10 with students, 7 with patients, 3 with parents/guardians, and 9 with other people such as pregnant women, homeless people, and refugees (Table 1).3,5,6,8,9,14-99

Table 1. Cognitive determinants of COVID-19 vaccine hesitancy
Author(s) Population & country Hesitancy rate Results Author(s) Population & country Hesitancy rate Results
Abedin, 2021213646 adults from
Bangladesh
8.5 % reluctant Confidence in the country’s healthcare systemAl-Sanafi & Sallam
202122
1019 HCWs from Kuwait9.0% The belief that the virus had a human-made origin
Adane et al, 202223404 HCWs from Ethiopia36.0% refused Anti-vaccine attitudes
Poor knowledge and perception
Al-Mistarehi et al, 2021
24
2208 individuals from Jordan -Lack of trust in the vaccine and their companies
Lack of enough information
Fear of side effects
Concerns about safety and effectiveness
Anti-vaccine attitudes
Adigwe, 2021251767 individuals from Nigeria-Concerns about side effectsAlrajeh, et al, 202126401 adults from KSA-Perceived susceptibility
Perceived benefits
Perceived barriers
Concerns about effectiveness, safety, false vaccination, and side effects
Aemro et al, 202127440 HCWs from Ethiopia45.9% hesitate Unclear information provided by public health authorities
Low perceived threat
Concerns about side effects
Alzubaidi, 202128669 students from UAE31.8%
hesitant
Risks perception versus vaccine benefits
Concerns about safety and effectiveness
Attitudes about the disease and its consequences
Knowledge and awareness about the vaccine
Personal, family, and community experience with vaccination and feelings of solidarity
Perception of the pharmaceutical industry
Lack of confidence in government policies
Afzal et al, 2022293759 HCWs from the US -Concerns about rushed vaccine development
Fear of side effects
Lack of trust in the people advocating for the vaccines
Anti-vaccine attitudes
An et al, 202130854 students from Vietnam-Concerns about side effects, safety, effectiveness, and rushed vaccine development
Fear of needles
Low perceived susceptibility
Lack of confidence in government
Aguilar Ticona et al, 202131985 non-pregnant participants from Brazil26.1% were hesitant and
7.9% unsure
Concerns about effectiveness and side effectsAshok et al, 202132264 HCW from India-Concerns about rushed vaccine development
Lack of enough information
Al-Ayyadhi et al, 2021206943 adults from Kuwait74.3% hesitantConcerns about safety and side effects
Believing conspiracy theories
Badr et al, 2021331208 adults from the US526 people were hesitant Low perceived susceptibility
Perceived the vaccination process as being more convenient
Baccolini et al, 2021345369 students from Italy22% to 29% hesitancy rangedLow perceived susceptibility and severity
Concerns about safety and effectiveness
Concern for the emergency
Chaudhary et al, 202135410 patients and their attendants from Pakistan47.3% were hesitantLack of knowledge Understanding the way vaccines work
Concerns about vaccine efficacy, safety, and comfort in the vaccine administration
Balan et al, 2021361581 students from Italy8% undecided group Rushed vaccine development
Vaccine barriers outweigh benefits
Belief in natural immunity
Lack of trust in the vaccine
Lack of trust in the local and medical authorities
Costantino et al, 20215346 patients from Italy25.2% were hesitantFear of adverse events
Concerns about rushed vaccine development
Not afraid of COVID-19
Uncertain of vaccine efficacy
Blanchi et al, 202114417 patients from Europe, France, and Italy18.9% were hesitantConfidence in getting the vaccine easily
Concerns about side effects and efficacy
Lack of trust in scientists and the healthcare system
de Sousa Á et al, 2021376843 individuals from Portugal21.1% were hesitantPerceived high stress
Afraid of future repercussions of the disease
Vaccine Conspiracy Beliefs and misinformation
Bolatov et al, 202138888 students from Kazakhstan70.7%-75.5%Trust in the opinions of close relatives
Concerns about side effects, safety, effectiveness, and quality
Belief in natural immunity
Du et al, 2021393011 reproductive women from China8.44% children and 3,011 reproductive women were hesitant Low perceived susceptibility
Lower perceived benefit
High perceived barriers
Bou Hamdan et al, 202140800 students from Lebanon 10% were hesitant Concerns about vaccine safety
The vaccine in agreement with their personal views
Agreement with conspiracies
Level of knowledge about COVID-19 disease and vaccine
Disagreement with that symptomatic cases are the only carriers of SARS-CoV-2
Ebrahimi et al, 2021414571 adults from
Norwegian
10.46% were hesitant Perceived risk of vaccination
Belief in the superiority of natural immunity
Lack of confidence in government
Fear of infecting significant others
Butter et al, 2022421599 adults from the UK17.7% uncertain, 8.1% refuse Low perceived susceptibilityEhde et al, 202143359 Adults from the US20.3% were hesitantLow perceived susceptibility
Low trust in the Centers for Disease Control and
Concerns about side effects, vaccine approval process, and potential impact of the vaccine given their health conditions
El-Sokkary et al, 202144308 HCWs from Egypt41.9% were hesitantPerception for the severity of COVID-19
COVID-19 vaccine safety
Anti-vaccine attitudes
Ghaffari-Rafi et al, 202145359 adult patients from US-Concerns about vaccine safety
Self-perception of a preexisting medical condition contraindicated with vaccination
Fares et al, 202146385 HCWs
from Egypt
51% undecided
28% refused
Lake of enough clinical trials
Fear of side effects of the vaccine
Gomes et al, 2022473232 individuals from Portugal11% were hesitantFeeling agitated, sad, or anxious
Low or no confidence in the health services’ response
Perceived measures implemented by the government as inadequate
Low perceived susceptibility
Concerns about safety and effectiveness
Fedele et al, 202148640 individuals from Italy50%
not sure
Concerns about side effects, safety, and effectiveness
Opposition to vaccines
Other non-specific reasons
Griva et al, 2021491623 adults from Singapore9.9% were hesitantConcerns about side effects, safety, and rushed vaccine development.
Low perceived threat
Lack of trust in the vaccine
Low perceived benefits
Lower moral and subjective norms
Freeman et al, 2021505114 adults from UK16.6% unsure
11.7% hesitant
Beliefs about a COVID-19 vaccine
Mistrust
Hwang et al, 20215113021 individuals from Korea39.8% were reluctant or refused Concerns about safety and side effects
Complacency toward COVID-19
Awareness of the preventive guidelines
Lack of confidence in government
No fear of COVID-19
Genovese et al, 2022524116 individuals
from Italy
17.5% were doubtful.Lack of trust in the vaccine
Low perceived susceptibility
Fear of side effects
Hossain, et al, 2021531377 individuals from Bangladesh35.25% unsure
18.99% denied
Concerns about side effects, safety, and efficacy
Against the vaccination program
Afraid of taking injections
Belief in natural remedies
Gerretsen et al, 2021157678 adults from US and Canada The mean (SD) hesitancy 2.3/6.0 (1.6)Low perceived seriousness
Low perceived threat
Low perceived susceptibility
Mistrust in vaccine benefit
Preference for natural immunity
Lack of confidence in government
Risk propensity
Mistrust in others
The negative impact of COVID-19 on mental health
Hossain et al, 202161497 adults from Bangladesh41.1% were hesitantPerceived susceptibility and severity
Perceived benefits and barriers
Anti-vaccine attitudes
Subjective norm
Perceived behavioral control
Anticipated regret
Lack of trust in the vaccine
Complacent
Calculative
Collective responsibility
Jain et al,
202154
1068
students from India
10.6% were hesitantConcern about safety and efficacy
Lack of awareness regarding their eligibility for vaccination
Lack of trust in the government
Li et al, 2021552196 students from China41.2% were hesitantPerceived severity
Concerns about side effects and effectiveness
Kanyike et al, 202156600 students from Uganda30.7% were hesitantConcerns about side effects
Low perceived threat
Belief in acquiring immunity against COVID-19
Liddell et al, 202157516
refugees living from Australia
28.1% were hesitantTrust barriers
Lower logistical barriers
Attitudes relating to low control
The Risk posed by COVID-19
Khairat et al, 2022583142 adults from the US Mean (SD) 8 (2.83) hesitantLack of trust in the vaccine
Concerns about side effects
Lack of confidence in government
López-Cepero et al, 202181911 adults from the USMore than 6.5% no intent
11% unsure
Lack of trust in the vaccine
Unafraid of getting COVID-19
Not worried about getting COVID-19
Barriers to getting the vaccine
Concerns about efficacy, safety, and novelty
The rigor of vaccine testing
Lack of confidence in government
Knight et al, 202159762 individuals from UK22% were hesitantConfidence
Complacency
Convenience
Luk et al, 2021601035 individual from
China
29.2% undecided
25.5% no intention
Concerns about safety, side effects, and effectiveness
Knowledge of SARS-CoV-2 transmission
Perceived danger of COVID-19
Kucukkarapinar et al, 2021613888 adults from Turkey43.9%-58.9%
Increased rate of vaccine hesitancy/refusal
Conspiracy thinking
Less knowledge of prevention
Reduced risk perception
Higher perception of media hype
Trust in the Ministry of Health and medical professional organizations
Marijanovic et al, 202162364 patients from Bosnia and Herzegovina37.6% Not sureDoubt about the results of clinical trials of COVID-19 vaccines
Kuhn et al, 20211990 homelessness from the US48% were hesitantFear of side effects
Rejection of all vaccines
Less trust in COVID-19 information from official sources, media, and friends
Perceived threat
McCarthy et al, 20219779 patients from Australia30.6% were hesitantVaccine conspiracy theory
Having higher perceptions of anomie
Lack of confidence in government
Low perceived health threats
Lee & You 2022631016 individual from
South Korea
53.3% were hesitant Perceived susceptibility
perceived benefits
Perceived barriers
Lack of confidence in government
Moujaess et al, 202164111 Patients from Lebanon30.6% were hesitantDesire to know more about the consequences of the vaccine in other patients with cancer
Muhajarine et al, 2021659252 adults from Canada13 % were unsure, and 11% refusedLow perceived threat
Low perceived severity
Not concerned about spreading the virus
Orangi et al, 2021664136 individuals from Kenya36.5% were hesitantLow perceived threat
Concerns about side effects and effectiveness
Murphy et al, 202118Ireland = 1041 and UK = 2025 individual35% hesitancy for Ireland
31% hesitancy for England
Low trust in scientists, healthcare professionals, and the state
Negative attitudes toward migrants
Lower levels of altruism
Higher levels of conspiratorial
Lower levels of agreeableness
Higher levels of internal locus of control
Lower levels of the conscientiousness
Higher levels of neuroticism
Belief in chance
Beliefs about the role of powerful others
Patwary et al, 202167543 adults from Bangladesh15% were hesitantPerceived barriers
Subjective norms
Low perceived threat
Anti-vaccine attitudes
Less self-efficacy
Concerns about side effects and effectiveness
Lack of enough information
Belief in natural immunity
Navarre et al, 2021681964 HCWs
from French
46.6% opposition to vaccinationLack of trust in health authorities Park et al, 202169902 individuals from South Korea20.8 % were hesitantLow perceived threat
Concerns about safety
Affective and Cognitive risk perception of COVID-19
Perceived the government’s performance as ineffective
Nazlı et al, 202170467 18-65 years old from Turkey 13.2% were hesitantBelief in conspiracy theories low fear of COVID-19Paschoalotto et al, 2021711623 individuals from Brazil30% were hesitantConcerns about side effects
Nery et al, 2022722521 individuals from Brazil18.6% were hesitantLow perceived threatPedersen et al, 202116423 individuals from 31 countries4% were hesitantConcerns about side effects, rushed vaccine development, and effectiveness
Lack of enough information
Nguyen et al, 202173651 pregnant women from Vietnam-Concerns about safety and effectivenessPeirolo et al, 202174776 HCWs from Switzerland-Low perceived threat
Concerns about side effects
Okubo et al, 20217523142 individuals from Japan11.3% were hesitantConcerns about adverse reactions
Doubts about the vaccine efficacy
Low perceived susceptibility
Prickett et al, 2021761284 individuals
from New Zealand
14.2% were unlikely and 15.1% unsureConcerns about the side and future effects
Thought their chances of becoming seriously ill if they caught COVID-19 were low
Being protected by herd immunity
Rahman et al, 202177850 adults from Bangladesh30.23% were hesitant Afraid of side effects
lack of enough information
Lack of trust in the vaccine
Schernhammer et al, 2022781007 adults from Australia41.1% were hesitantOptimism
Reno et al, 2021791011 individuals from Italy31.1% were hesitantPerceived threatShekhar et al, 2021803479
HCWs from the US
56% were hesitantConcerns about Safety, efficacy, and rushed vaccine development
Roberts et al, 2022811004 adults from the US-Anti-vax beliefs Shen et al, 2021822361 individuals from China-Lack of trust in the vaccine
Risks perception
Ruggiero et al, 202183427 parents from the US21.93% were hesitantConcerns about side effects and safetySoares et al, 2021841943 individuals from Portugal56% wait and 9% refuse.Lack of trust in the vaccine and the health service response
Worse perception of government measures
Perception of the information provided as inconsistent and contradictory
Schaal et al, 2021852339 pregnant & breastfeeding from Germany Pregnant: 28.9% unsure
Breastfeeding: 28.1% unsure
Scientific data on the COVID-19 vaccination are too preliminary
Lack of enough information
Being anxious because of vaccine damage to the unborn or causing pregnancy Complications
Solak et al, 202286525 adults from Turkey-Need for cognitive closure
Sharma et al, 202187428 African Americans from US48% were hesitantPerceived Advantages
Perceived Disadvantages
Participatory Dialogue
Behavior Confidence
Spinewine et al, 2021881132 HCWs from
Belgium
37.1% were hesitantConcerns about side effects, rushed vaccine development, and effectiveness
Low perceived threat
Schwarzinger et al, 2021891942 adults from France71.2% were hesitantVaccine efficacy
Concerns about side effects
Communication about the collective benefits of herd immunity
Stojanovic et al, 20211732028 individuals from Brazil, Canada, Colombia, France, Italy, Turkey, UK, US27% were hesitant.
France had highest level of hesitancy (47.3%) and Brazil the lowest (9.6%)
Fewer COVID-19 health concerns
Higher personal financial concerns
Theis et al, 202190816 Wright-Patterson Air Force Base (WPAFB) from the US22.7% Concerns about side effects and effectiveness
Vaccines making them feel sick
Vaccine infects them COVID-19
Being worried about misinformation/political agenda
West et al, 202191360 Temporary Foreign Workers from Bangladesh25% were hesitantFear of side effects
Low perceived threat
Willingness to take the vaccine by more people first
Lack of enough information
Ticona et al, 202192985 individuals from Brazil26.1% were hesitant Concerns about effectiveness and side effectsWu et al, 202293306 adult
from the US
33.99% were hesitantConcerns about side effects, safety, ingredients, rushed vaccine development, and effectiveness
Low perceived threat
Concerns about vaccine causing MS relapse, making MS medication ineffective, and getting the COVID-19 infection
Prior bad experiences with other vaccines
Tram et al, 20213459235 households from the US10.2% “probably NOT” get a vaccineConcern about side effects and safety
Other people need it more than I
Lack of trust in the vaccine
Lack of confidence in government
Xu et al, 2021944748 parents from China25.2% of women, 26.1% of their spouses, and 27.3% of their children Psychological distress
Concern about safety
Turhan et al, 202195620 individuals from Turkey-Lack of trust in healthcare system Yanto et al, 202196190 adults from Indonesia13.2% were hesitantAgreeableness trait
Neuroticism
Lack of confidence in government, scientists, and HCWs
Wang & Zhang 202197382 parents from China -Psychological flexibility
Self-efficacy
Coping style
Zhang et al, 2021981015 individuals from China82 Doubtful 39 Strongly Hesitancy Conspiracy beliefs
Medical mistrust
Knowledge of vaccines
Vaccine confidence and complacency
Wang et al, 2021997318 adults from China67.6% were hesitant Confidence
Complacent
Convenience
----

HCWs: health care workers.

Risk of bias

On average the studies met 68.5% (range = 51-86%) of the rating criteria. On the whole, the studies showed a moderate risk of bias, and more than half of them (n = 63; 69%) were of good quality (range = 70 to 85).

Variations in vaccine hesitancy and refusal

Vaccination hesitation rate varied from 4% among patients with primary ciliary dyskinesia16 to 74.3% (mean = 29.72) in people over 18 years of age living in Kuwait20 and reported refusal rates were 8.6% to 75.5% (mean = 26.88). In addition to the hesitancy rate, some studies also measured uncertainty (mean = 23.25), undecided (mean = 29.4), and reluctance (mean = 24.15).

Cognitive Determinants of COVID-19 Vaccine Hesitancy

Among the evaluated peer-reviewed literature, based on a collective sample of 1 335 139 participants, several categories of cognitive determinants were extracted:

5C Psychological Antecedents

A number of studies have used in a way five factors of confidence, complacency, constraints, calculations, and collective responsibility, which are known as 5C psychological antecedents.3,5,6,8,9,14-16,20,21,24-36,38-44,46-63,65-77,79,80,82-84,88,89,91-93,94-98 Confidence and complacency in the vaccine were two of the most frequent variables used by most studies. We categorized the concerns about probable vaccine side effects, vaccine effectiveness, the rapid procedure of vaccine manufacturing, and lack of trust in the efficiency of some brands under the perceived confidence of participants about the COVID-19 vaccine. In addition, perceived threats, including perceived susceptibility and severity, the risk posed by COVID-19, and risk propensity, were categorized as complacency.

Perceived self-efficacy and perceived behavioral control

According to studies, individuals with higher general self-efficacy and specific self-efficacy of preventing COVID-19 displayed stronger intentions to get vaccinated.67,97 In addition, in relation to perceived behavioral control, Hossain et al found that the respondents who registered voluntarily for COVID-19 vaccination had been less vaccine-hesitant.6

Perceived locus of control

Murphy et al used the locus of control variable as a psychological indicator of COVID-19 vaccine acceptance/hesitancy/resistance.18 They measured internal and external locus of control among Irish and England participants. Their results indicated that in the Irish and UK, vaccine hesitant/resistant people felt more control over their lives, acted based on their preferences, and had higher levels of internal locus of control.

Inhibiting subjective norms

Social/peer influence was the variable that some studies applied as a predictor of COVID-19 vaccination hesitancy.6,49,67 The results of their studies have shown that vaccine hesitancy tended to decrease with the increase of perceived subjective norms.

Anti-vaccine beliefs

We found that conspiracy theories concerning the COVID-19 vaccine have a significant impact on decision to hesitate. For example, some related beliefs were as follows: (i) Vaccine protection against COVID-19 is temporary; (ii) COVID-19 vaccines modify DNA; iii) the vaccine can induce other disorders such as autism or autoimmune diseases; (iv) COVID-19’s vaccine has chips implanted to control people; (v) the vaccine’s efficacy and published studies are untrue37; (vi) The virus is manufactured by humans ; (vii) the virus’s spread is an deliberate attempt to reduce the global population’s growth; and viii) COVID-19 is a biological weapon produced by China to crush the West.50

Stress and anxiety

Perceived stress has been used as a factor associated with COVID-19 vaccine hesitancy by de Sousa et al in Portuguese-speaking countries. They found a significant direct relationship between vaccine hesitancy and perceived stress.37 According to Xu et al, parents with psychological distress are more likely to hesitate to vaccinate for themselves, their spouses, and their children.94 Feeling agitated, sad, or anxious were other factors that were shown to be associated with vaccine hesitancy in a survey conducted by Gomes et al.47

Fears and concerns

Some studies reported fears such as fear of needles and injection,30 fear of infecting significant others,41 and higher personal financial concerns/fear of the expensive vaccination costs, which make people hesitate to adopt the COVID-19 vaccination. Additionally, the Ghaffari-Rafi et al study showed that patients with an insight into a preexisting medical condition believed that COVID-19 vaccination might threaten their health because of existing disease.45

Optimism

Optimism indicates the extent to which people hold positive expectancies for their future100 used by Schernhammer et al. They explored the correlation of optimism with hesitancy toward COVID-19 and reported that persons with medium to high optimism were less prone to vaccine-hesitancy.78

Personality traits

Some personality traits such as personal anomie, altruism, conscientiousness, agreeableness, and neuroticism have been used by several studies9,18,96 as psychological indicators of vaccine hesitancy. These studies indicated that higher levels of neuroticism, perceptions of anomie, and lower levels of agreeableness, conscientiousness, and altruism might influence the increase in COVID-19 vaccine hesitancy.


Discussion

This systematic review aimed to investigate the cognitive determinants of COVID-19 vaccination hesitancy. We discuss several cognitive factors that may play a role in COVID-19 vaccine hesitancy.

Confidence and complacency, two antecedents of the 5C psychological model, were among the most common cognitive factors studied to explain COVID-19 vaccine hesitancy. The confidence was relevant to trust in the government’s decisions, the effectiveness of the vaccines, and the COVID-19 Vaccine delivery system.101 Confidence in the COVID-19 vaccine and concerns about its safety have been reported in most studies.5,14,20,29,31,38 According to studies, concerns about the probable side effects of the vaccine, its ingredients, its effectiveness, and safety, as well as the rapid process of vaccine production and the vaccines approval process, reduce the trust of people in the COVID-19 vaccine. Although most of the side effects of COVID-19 vaccines have been confirmed scientifically, some are undocumented or have fewer shreds of evidence. This can lead to insufficient knowledge, the formation of improper beliefs, incorrect information, and mistrust in vaccines.102

When a vaccine is quickly produced and distributed, information sources such as the Internet and other social media disseminate claims about its harms and ineffectiveness.103,104 Much of this information may exaggerate risks associated with the COVID-19 vaccines105 and could cause the formation of anti-vaccine conspiracy beliefs.106,107 Most of the information that is published by unreliable sources targets the safety of vaccines, worries people about short-term adverse reactions and possible long-term effects of the COVID-19 vaccine, and can ultimately lead to hesitation and refusal to vaccinate.105

On the other hand, confidence in vaccines can result from people’s trust in the public health care system and in delivering safe and effective vaccines.101 In this regard, the WHO vaccine advisory group highlights the role of healthcare workers in building confidence in COVID-19 vaccines. Because healthcare providers can be effective in improving people’s insights and awareness about the benefits of vaccination and addressing people’s concerns about newly developed vaccines.108

The role of distrust of the government and health care system is significant in causing vaccine hesitancy.28,30,41,97 Usually, people are worried about the side effects of vaccines imported to the country or manufactured there, which may lead to a lack of trust and fear about vaccines. 7 The lower the people’s trust in the government, the more risk perception of the threat. Therefore, governments should provide safe vaccines.69 In fact, trust in the government and health authorities is essential for vaccine acceptance, especially in cases such as COVID-19, where anxiety about the nature of the disease is significant.101

When the nature of a disease is not completely clear, the chance of spreading conspiracy beliefs may increase, and it was recognized that in the COVID-19 pandemic, the growth of conspiracy beliefs and the reduction of people’s participation in vaccination have occurred.9 Conspiracy theories explain the negative emotions and uncertainty that traditionally increase during times of social crisis (such as war, environmental disaster, and terrorism). In this situation, uncertainty, powerlessness, and fear and anxiety increase.9 With the rapid prevalence of the COVID-19 pandemic, a wide range of conspiracy beliefs emerged and spread. For example, COVID-19 is a hoax, a biological weapon developed by the Chinese, and the COVID-19 vaccine microchips will be injected to control COVID-19,9,109 which indicates that the vaccine manufacturing companies underestimate the side effects of the vaccines.9 The development of such beliefs may cause mistrust and reduce the vaccination acceptance rate. Therefore, delivering information that focuses on the effectiveness and safety of the COVID-19 vaccine from reliable sources can be influential in reducing vaccination hesitancy.

The second antecedent of 5c psychological is complacency. More complacency is defined as a lower perceived threat of disease and the belief that vaccination is unnecessary as a preventive measure. In other words, people with high complacency have more feelings of invulnerability and less preventive behavior than those with low complacency.101 According to the Health Belief Model (HBM), people are most likely to take a preventative behavior when they perceive the threat of disease. The HBM is one of the most widely used models to explain vaccination behavior.6,110 Studies have shown that worrying about getting infected with COVID-19 and believing in the seriousness of its consequences can persuade people to get the COVID-19 vaccine.6,111 Also, the newer fourth-generation models, such as the multi-theory model of health behavior change, have underscored the role of getting convinced of the advantages of behavior change over the disadvantages and building behavioral confidence.87

One of the important factors in getting the vaccine is the perceived benefits of a vaccine. Such as the belief in its protective effect against COVID-19 and its subsequent side effects are among the influential factors in adherence to the COVID-19 vaccine.111 In contradiction of that, perceived physical and psychological barriers that can make the vaccine an unpleasant experience 21,111 and concerns about safety and its probable side effects, fear of needles, and its costs can increase vaccination hesitancy.112,113

Locus of control and belief in chance were other cognitive factors recognized in this study. Health locus of control refers to the degree to which a person believes that he/she, as opposed to external forces, has control over his/her health. Locus of control is conceptualized as internal or external.114 The internal dimension is positively associated with engaging in health behaviors, and chance as the external dimension is positively related to non-adherence to health behaviors.115 People whose health locus of control is external may be doubtful about how to behave in a healthy manner,116 such as vaccination, and it is reported that the external locus of health control is related to a lower level of childhood vaccination through parental attitudes.

Studies have used self-efficacy and perceived behavioral control as predictors of COVID-19 vaccine hesitancy.6,67,97 As self-efficacy reflects one’s belief in their ability to perform a particular behavior,110 like the COVID-19 vaccination, perceived behavioral control similar to self-efficacy also refers to the person’s belief that the considered behavior is under control. As a result, most psychosocial health behavior theories postulated that self-efficacy and perceived behavioral control had been introduced as major determinants of engaging in health behavior.110 Also, the role of behavioral confidence has been underscored in the newer fourth-generation models, such as the multi-theory model (MTM) of health behavior change.


Limitations

Due to resource constraints needed to translate and retranslate studies published in other languages, the investigation was limited to manuscripts published in English only. Hence the results are not representative of research published in other languages. Further, the search in this review was limited to the title, keywords, and abstract of each publication. Perhaps more in-depth search could have resulted in identification of more studies. A single statistical analysis of the data was not practical or feasible because of the sizable variability in the cognitive determinants of COVID-19 across studies. Therefore, a narrative analysis was accomplished, thereby limiting the external validity of the conclusions.

Implications for practice and future research

Given that hesitancy and distrust of a new health product and service such as the COVID-19, vaccine will always exist, the development of strategies that can build trust in people to vaccinate and improve the government’s ability to manage and successfully implement mass vaccination calls for attention. According to studies, several factors can contribute to building trust117:

Responsiveness: Health authorities should show competence in responding to people’s health needs, fears, and concerns by establishing a transparent and coherent relationship about the vaccine quality. Qualitative research can help identify people’s needs, concerns, and fears about the COVID-19 vaccination.

Openness: The public must understand the importance of rapid vaccine production and distribution to achieve herd immunity during new epidemics. Also, more importantly, people should ensure that no quality or safety standards have been sacrificed for speed in the vaccine production process. Therefore, people should be informed about all phases of production, approval, evaluation, and distribution of vaccination through a proper communication strategy. Paying attention to myths, misconceptions, and false information about vaccination, monitoring the messages of widely used social media such as the Internet, spreading correct information through the creation and introduction of reliable information sources, and increasing health literacy and e-health literacy of people are other strategies for considering openness.

Reliability, integrity, and fairness: Holding campaigns to encourage people to take the vaccine with the presence of health authorities, pioneering them in receiving the vaccine, and providing information about all the benefits and harms of the vaccine, will increase confidence in the vaccination.


Conclusion

COVID-19 vaccine hesitancy as a significant challenge for public health has been reported in many countries. Our findings highlight the importance of understanding the cognitive factors contributing to COVID-19 vaccine hesitancy to develop effective health communication programs for persuading people toward COVID-19 vaccination and the most common reason for vaccine hesitancy was a lack of confidence and complacency. Multiple factors, including concerns about vaccine safety and side effects, perceived susceptibility and severity, the risk posed by COVID-19, and risk propensity, could influence delay or refusal to accept the vaccine. Information through trusted sources to reduce hesitancy about the COVID-19 vaccination.


Competing Interests

Hamid Alahverdipour is Editor-in-Chief of the Health Promotion Perspectives. Other authors declare no competing interests.


Ethical Approval

This research was performed based on Tabriz University of Medical Sciences ethics committee approval (Approval ID: IR.TBZMED.REC.1400.564).


Funding

This study was supported by Tabriz University of Medical Sciences, Tabriz, Iran. The funders had no role in study design, data collection and analysis, the decision to publish, or the preparation of the manuscript.


Supplementary Files

Supplementary file 1 contains search strategy applied to the PubMed database.


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Submitted: 24 Mar 2023
Revised: 26 Mar 2023
Accepted: 27 Mar 2023
First published online: 30 Apr 2023
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