Factors Influencing Public Attitudes towards COVID-19 Vaccination: A Scoping Review Informed by the Socio-Ecological Model

Major hindrances to getting a COVID-19 vaccine include vaccine hesitancy, skepticism, refusal, and anti-vaccine movements. Several studies have been conducted on attitudes of the public towards COVID-19 vaccines and the potential influencing factors. The purpose of this scoping review is to summarize the data available on the various factors influencing public attitudes towards COVID-19 vaccination. This scoping review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR) Statement. PubMed, Embase, Web of Science, and Cochrane Central were searched without restrictions to reclaim all publications on the factors that shape individuals’ attitudes towards COVID-19 vaccines from 1 January 2020 to 15 February 2021. Fifty studies were included. The scoping review revealed that the factors influencing public attitudes towards COVID-19 vaccines were embedded within the different levels of the socio-ecological model. These factors included the sociodemographic characteristics of the individuals, individual factors, social and organizational factors. In addition, certain characteristics of COVID-19 vaccines themselves influenced public attitudes towards accepting the vaccines. Understanding various population needs and the factors shaping public attitudes towards the vaccines would support planning for evidence-based multilevel interventions in order to enhance global vaccine uptake.


Introduction
Coronavirus disease 2019 (COVID-19) is a contagious and pathogenic viral infection caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a specific type of coronavirus that was first discovered in Wuhan, China [1]. It was declared a global pandemic by the World Health Organization on the 11 March 2020. The pandemic caused by COVID-19 has infected more than 125 million people and killed at least 2.5 million globally and is becoming a leading cause of death [2]. This virus has become a major concern around the globe, having so many consequences on the healthcare system and economy and instilling fear in communities [3,4]. The main mode of transmission is through droplets, direct contact with infected patients; it can also be transmitted through fomites, by touching contaminated surfaces or objects [5]. People who are at increased risk of getting severe infection include the elderly and those who have chronic diseases [6].

Eligibility Criteria
In this scoping review, all the articles published between 1 January 2020 to 15 February 2021 about the factors that shape public attitudes towards COVID-19 vaccines were included. The articles selected were only in English, with human subjects aged 16 years and above, excluding healthcare workers who are obligated to get a vaccine. Articles were only included in English since it was the major language of the available articles in the databases at the time this search was conducted.
Two authors independently screened abstracts and citations retrieved from the search and each author (out of the seven authors) was given a specific number of articles to assess full texts of the relevant records to be included in the review. When dealing with duplicates, the most recent version of the article with the largest sample size was included. During the study selection and assessment process, the first author was responsible for resolving any disagreements and final evaluation.

Data Charting Process
The relevant data were abstracted from the eligible articles in pre-structured data charting forms (Excel (Microsoft Corporation, Redmond, WA, USA) and Word (Microsoft Corporation, Redmond, WA, USA) documents). The following information was included: the first author of the study, publication year, study design, population, study setting, mean age of the participants (in years), sample size, attitude towards COVID-19 vaccines, and the various factors shaping these public attitudes. Descriptive statistics (percentages) were reported for some studies to reflect the rate of positive or negative attitudes towards the vaccines. The final column in the table reported percentages to reflect prevalence of the factors shaping the attitudes, and for some studies, the p-value was reported to reflect the significant association between the factors and public attitudes towards the vaccines.

Synthesis of Results
Description of the scope of literature was presented in tables according to the key levels of the socio-ecological model [22] which showed how a health determinant (public attitudes towards COVID-19 vaccines) can be influenced by the various factors embedded in different levels. In our review, we summarized and clustered the factors that influenced public attitudes towards COVID-19 vaccines into sociodemographic characteristics, individual factors, and social and organizational factors. The final set of factors that were related to the specific characteristics of COVID-19 vaccines were summarized and reported in a separate table.

Data Analysis
Outcome data related to the factors that influence public attitudes towards COVID-19 vaccines were summarized and clustered into the different levels of the socio-ecological model. Meta-analysis was not performed due to heterogeneity in the contextual and environmental factors including the healthcare system in the countries of the selected studies in our review.

Results
In total, 331 records were retrieved from the electronic database search. The remaining records, after removing the duplicates, amounted to 274 records. After screening the titles and abstracts, 185 were excluded; the remaining 89 full-text articles were assessed for eligibility, and 50 studies were reserved for this review. The PRISMA diagram illustrates the study selection process and shows the reasons for exclusion for other studies (Figure 1).

Study Characteristics
The studies were divided by design into one experimental study [23], 39 cross-sectional studies , five literature reviews [63][64][65][66][67], one systematic review [68], one randomized controlled trial [69], one longitudinal survey with two experiments [70], one Gallup panel [71], one media analysis study through a proposed novel behavioral dynamics model SRS/I (susceptible-reading-susceptible/immune) for the microblogging platform Weibo on social media [72], and one conference paper [73]. The majority of these crosssectional studies reported their findings from one country, one study reported data from 19 countries [25], another study conducted legal analysis for several countries [40], and others reported findings from two or three countries from Europe, America, Canada, and the Middle East [29,49,59]. The sample size of the reviewed studies ranged from 101 participants in an RCT study [69] to 13,426 participants in a survey conducted in 19 countries [25].
An online (web-based) survey was the most common data collection method applied in the cross-sectional studies in our review, of which: − Some studies reported using social media platforms including Facebook, Twitter, and LinkedIn to collect data [26,38,41,62,72]; − Some studies reported using specific platforms to upload surveys including crowdsourcing platform Amazon Mechanical Turk (mTurk, Amazon, Seattle, WA, USA) [32,61], computer-assisted web interviewing (CAWI) and computer-assisted telephone interviewing (CATI) [34,53], and Qualtrics (Seattle, WA, USA) [47,55]; − One study used an online questionnaire to examine public attitudes towards COVID- 19 vaccines in three phases: pre-lockdown, during lockdown, and post lockdown with different participants in every phase [41], and another study conducted two-wave follow-up online surveys [55]; − One study used an online survey with a semi-structured questionnaire following the snowball sampling technique [60]; − One study used open-ended questions to ask about the factors influencing attitudes towards vaccines [47]; − One study used an Internet survey and telephone interviews [35]; − One study used a face-to-face-administered questionnaire [37].
The target populations in the majority of the reviewed articles were adults from the general public. The youngest participants were recruited in a study from Italy in which the age ranged from 15 to 85 years [53], and another study was conducted among parents and guardians aged 16 years and above who reported living in England with a child aged 18 months or under [26]. Only three studies were conducted among populations with specific demographics such as the working population in Hong Kong (HK), China [52], people with respiratory chronic diseases and older adults aged 65 and above [47,55], and the black American community in an RCT study [69].
The reported vaccine acceptance rate in the reviewed articles ranged from 29.4% to 86% [23,24,26,[45][46][47][48][49]51,72]. A study from the Middle East [49] reported a low rate of acceptance among the public from Jordan, Kuwait, and Saudi Arabia (29.4%), while a higher acceptance of 53.1% was reported in a study from Kuwait [48]. On the other hand, 86% of people in the UK expressed their willingness to receive a vaccine [47]. The information on the baseline characteristics of the selected studies can be found in Table 2.

Individual Factors Shaping Public Attitudes towards COVID-19 Vaccines
Jung, H. 2020 [70] + -Prosocial concern for vaccination motivates vaccination in more and less populated regions

Individual Factors Shaping Public Attitudes towards COVID-19 Vaccines
Largent, E.A. 2020 [71] − -Republicans and Independents were less likely to get vaccinated than Democrats Ward, J.K. 2020 [54] Attitudes to a COVID-19 vaccine -Political partisanship and engagement with the political system Romer, D. 2020 [55] − -Belief in three COVID-19-related conspiracy theories Our review showed that the individuals who believe that coronavirus is contagious and lethal, have good knowledge and score high on health literacy, are stressed, worried, and anxious about getting infected, trust the healthcare system, the government, and the companies producing the vaccines, and have positive experience with previous vaccines were more likely to accept COVID-19 vaccines than others. On the other hand, the individuals with greater conspiracy beliefs and political conservatism, and those with personal reasons to refuse a vaccine, including religious conviction, were hesitant and reported negative attitudes towards COVID-19 vaccines. Table 5 represents the articles that discussed the role of family, friends, healthcare providers, and employers in shaping public attitudes. In addition, it depicts the articles discussing the role of traditional (classic) and social media. Social networks and organizational factors that affect the attitude toward COVID-19 vaccines were reported in 10 studies. Social service and healthcare providers and the physician's recommendation of vaccination [28,43,44,69] were the most prevalent ones. The individuals who were advised by a physician or any other healthcare provider to take a vaccine were more likely to have a positive attitude towards it than those who did not get any advice. The employer's recommendation might also influence an individual's attitude positively [25]. Table 5. Social and organizational factors associated with hesitancy or acceptance of COVID-19 vaccines. The influence of traditional media [42], type of messages received, and disinformation through the Internet and social media [23,37,64] were among the reported factors. The reviewed articles showed that misleading information shared on social media platforms would make individuals hesitant to take the vaccine. In addition, 78% of the participants in one study stated that their decision to get a vaccine was supported by their family and friends [31], especially when someone of their family members or friends was vaccinated [44]. Table 6 summarizes the literature that shows how some vaccine characteristics affect public attitudes. Efficacy [28,40,43,45,46,63,65,68,73], safety [25,28,35,47,63,65,68,73], cost [46,63,68,72], and adverse effects or toxicity of the vaccine [37,40,46,47,63,68,72,73] were among the vaccine characteristics that were reported to shape public concerns about COVID-19 vaccines. The reviewed articles showed that the individuals who had a negative perception towards vaccine efficacy, safety, and side effects would report unwillingness and hesitancy towards taking a vaccine.

Characteristics of COVID-19 Vaccines Shaping Public Attitudes towards COVID-19 Vaccines
Lin, Y. 2020 [ Furthermore, immunity duration [68], timeframe of vaccination [63], fake or lowquality vaccines [46], country of vaccine origin [24,68] and information about inactivated vaccines [72] were other public concerns in the selected studies. The individuals who believed that immunity boosted by a vaccine would be for a short period, vaccine development was expedited, and the production process was pushed, and that the vaccines are most probably fake would report negative attitude towards COVID-19 vaccines.

Discussion
This scoping review of 50 articles systematically maps evidence on the influencing factors that may lead to COVID-19 vaccine hesitancy worldwide. Vaccine hesitancy and antivaccination movements represent an old phenomenon that threatens global health [74][75][76][77]. With the current situation of the COVID-19 pandemic, this can be a stumbling block in the global efforts to control the disease and its devastating consequences.
Vaccination is considered a vital element for public health; it is the most effective intervention for the primary prevention of communicable diseases. To enhance acceptance and uptake of vaccines, it is crucial to gain insight into the common factors that influence an individual's decision-making process to help inform policymakers to develop effective strategies. This scoping review updates the latest information on the determinants that impact COVID-19 vaccine uptake. The review included studies that reported global data which offer an insight on how public attitudes towards COVID-19 vaccination varies around the world. It also demonstrated that these attitudes are influenced by a wide range of factors on multiple levels of the socio-ecological model. Sizeable evidence showed that sociodemographic factors such as age, gender, and income status, individual factors such as personal beliefs and risk perception, and social and organizational factors such as the role of significant others are among the most related determinants. In addition, certain characteristics of the COVID-19 vaccines themselves like efficacy, safety, and side effects influence public attitudes (Table S1).
The individuals' attitudes towards the COVID-19 vaccination varied among the studies, with acceptance ranging from 29.4% to 86%. This discrepancy could be attributed to variations in the study population. Sallam et al. [49] reported a very low rate of acceptance among people in three Arab countries, Jordan, Kuwait, and Saudi Arabia (29.4%), as compared to a relatively higher acceptance of 53.1% reported in one study in Kuwait [48]. In contrast, as high as 86% of people in UK (mainly elderly and middle-aged at-risk adults) expressed their willingness to receive a vaccine [47]. This is in line with the findings of a recent systematic review [77] that showed a global variation in the rate of vaccine acceptance, with the Middle East being among the regions having the lowest rates. The review related this finding to the widespread embrace of conspiratorial beliefs in the region, which subsequently resulted in negative attitudes towards vaccination. This negative attitude in the Arab region is alarming.
Assessment of the role of gender in COVID-19 vaccine hesitancy revealed that men are more willing to accept the vaccine than women [28][29][30]38,48,49], and this held true across cultures (Arab countries [48,49], China [28], Ireland, and the UK [29]). Only one cross-sectional study in the USA reported lower acceptance among men [32]. Women were reported to have adopted more negative views about vaccination [30] while men showed a lower belief in rumors and conspiracy theories surrounding COVID-19 and higher risk perception for the disease [49,77]. However, this finding should be interpreted with caution in light of sex distribution, as sampling bias cannot be ruled out.
Similar to previous findings, the current review found variations in vaccine acceptance and uptake across different race and ethnic minorities. Blacks, Hispanics, Chinese, Asian, non-Irish, mixed, or other ethnicities were more hesitant and more likely to reject the vaccines. The literature attributed this attitude to religious and cultural beliefs, norms, and concerns [37,79]. High education level and high-income status were associated with positive attitudes toward vaccination, owing to minimal barriers related to knowledge, health literacy, and cost concerns [23][24][25]27,30,35,36,42,47,[49][50][51]63,65].
In addition, other factors were included, such as health condition, people with chronic diseases, occupation status, marital status, place of residence, women being pregnant or having children, and having health insurance or not. More willingness and acceptance were reported among married individuals [7,28,52], those who reside in rural or suburban areas [29,68], being employed [27,46,50,53,73], especially in professional and managerial occupations [50,53], being at risk or belonging to a vulnerable group [34,45,65], and having insurance [30,31,36,51,68]. Knowing these factors can provide guidance for organizations and professionals on people and settings that need to be targeted to enhance vaccine acceptance and improve vaccine uptake rates [79].
Several studies examined the role of the social network and organizational factors [24,25,28,31,37,[42][43][44]64,69]. Healthcare professionals appeared to be a trusted source of information. Their recommendations [28,43,44,69] in addition to support of family and friends [31,44] play an important role in shaping perceptions and behaviors towards vaccination. Significant others were reported in the literature to influence one's attitude and behavior. Information, acknowledgement, and recommendations from family members, friends, employers, and community members were associated with favorable attitudes and a higher uptake of vaccines [25,78,80].
On the other hand, the misinformation encountered, particularly on social media, the type and frame of massages received may influence the attitude to vaccination and intention [24,37,42,64]. Propagation of myths and conspiracy theories around vaccines and promotion of the antivaccine sentiment, combined with exposure to persuasive tactics, can convince the person that the vaccine is harmful, as indicated by Sarah Ashfield et al. [81]. Accordingly, public health organizations, healthcare professionals, and media platforms can collaborate to guarantee information accuracy, deliver health promotion programs to improve levels of health literacy to enable the target population to make an informed decision. In addition, this psychosocial environmental impact implies that strategies to overcome hesitancy can be framed within models that consider these multifaceted and multileveled factors.
Beyond these, the present review also found other factors that further contribute to our understanding of the barriers to vaccination uptake. Immunity duration [68], vaccination timeframe [63], fake or low-quality vaccines [37,46], beliefs about the consequences [47], country of vaccine origin [68], information about inactivated vaccines [72], and doubts about technology used in production [37,67] allow a detailed understanding of how to approach vaccine-hesitant groups to increase acceptance and uptake of the vaccines. These concerns can be addressed via awareness campaigns guided by physicians and other healthcare professionals to foster trust in health authorities, assure the public, and illustrate the role of vaccination in acquiring herd immunity and preventing disease transmission.
As illustrated above, the majority of the studies in this review addressed factors associated with vaccination attitude at the micro-meso level; however, there is a lack of publications that address the factors on the upper level of the socio-ecological model. Determinants on the macro-level of the model, including policy/regulations, broad sociocultural, religious, political, and environmental factors, and the influence they may exert on COVID-19 vaccine uptake are underexplored to date, at least in the results presented in our review. This gap in evidence necessitates further research to comprehensively tackle the issue of vaccine hesitancy. Another important output for this scoping review reflects the gap in clinical evidence concerning the COVID-19 vaccine efficacy, safety, and side effects to date, which showed an influence in shaping public hesitancy and refusal of the vaccines. Clinical research is needed to fill this gap and manage sharing evidence that will alleviate public concerns and enhance vaccine acceptance.
The included studies reported global data which can be seen as a strength of this review. On the other hand, our review has some limitations. Only the articles in English were included; this may have potentially introduced bias or resulted in missing important literature. We did not include one keyword, "Antivax," in our search strategy; however, when we did, only one new publication was found, therefore, this would unlikely have a noticeable effect on our results. The majority of the included studies are cross-sectional, which limits the ability to infer the causation between the various factors and public attitudes towards the COVID-19 vaccination. Most of these studies used self-administered surveys that may lead to biases. Furthermore, uncontrolled health conditions of the target populations and the various global healthcare systems in the studies included in this review may have had a misleading influence on the results.
Understanding various population needs and the factors shaping public attitudes towards the vaccines would support planning for evidence-based multilevel interventions in order to enhance the vaccine uptake globally. In our findings, we were able to report factors on the individual, social, and organizational levels. Future research should focus on exploring the cultural, economic, and political factors influencing public attitudes towards the COVID-19 vaccination.

Conclusions
This review highlights the complexity of the topic. Our findings show that attitudes toward COVID-19 vaccines is shaped by factors that are multifaceted and multileveled. A combination of a set of complementary multilevel interventions and engagement of diverse players, recipients, and settings may be helpful to improve the vaccination uptake to win the fight against this pandemic.  Provide an explicit statement of the questions and objectives being addressed with reference to their key elements (e.g., population or participants, concepts, and context) or other relevant key elements used to conceptualize the review questions and/or objectives. 3

Protocol and registration 5
Indicate whether a review protocol exists; state if and where it can be accessed (e.g., a Web address); and if available, provide registration information, including the registration number.

Eligibility criteria 6
Specify characteristics of the sources of evidence used as eligibility criteria (e.g., years considered, language, and publication status), and provide a rationale.

3
Information sources * 7 Describe all information sources in the search (e.g., databases with dates of coverage and contact with authors to identify additional sources), as well as the date the most recent search was executed.
3 Search 8 Present the full electronic search strategy for at least 1 database, including any limits used, such that it could be repeated. 3 Selection of sources of evidence † 9 State the process for selecting sources of evidence (i.e., screening and eligibility) included in the scoping review.
3 Data charting process ‡ 10 Describe the methods of charting data from the included sources of evidence (e.g., calibrated forms or forms that have been tested by the team before their use, and whether data charting was done independently or in duplicate) and any processes for obtaining and confirming data from investigators.

Data items 11
List and define all variables for which data were sought and any assumptions and simplifications made. If done, provide a rationale for conducting a critical appraisal of included sources of evidence; describe the methods used and how this information was used in any data synthesis (if appropriate).

Synthesis of results 13
Describe the methods of handling and summarizing the data that were charted. 4

Results
Selection of sources of evidence 14 Give numbers of sources of evidence screened, assessed for eligibility, and included in the review, with reasons for exclusions at each stage, ideally using a flow diagram.

5
Characteristics of sources of evidence 15 For each source of evidence, present characteristics for which data were charted and provide the citations.

6
Critical appraisal within sources of evidence 16 If done, present data on critical appraisal of included sources of evidence (see item 12). NA

Results of individual sources of evidence 17
For each included source of evidence, present the relevant data that were charted that relate to the review questions and objectives. 8

Synthesis of results 18
Summarize and/or present the charting results as they relate to the review questions and objectives.

Summary of evidence 19
Summarize the main results (including an overview of concepts, themes, and types of evidence available), link to the review questions and objectives, and consider the relevance to key groups.

28
Limitations 20 Discuss the limitations of the scoping review process. 30

Conclusions 21
Provide a general interpretation of the results with respect to the review questions and objectives, as well as potential implications and/or next steps.

Funding 22
Describe sources of funding for the included sources of evidence, as well as sources of funding for the scoping review. Describe the role of the funders of the scoping review. 31 JBI = Joanna Briggs Institute; PRISMA-ScR = Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews. * Where sources of evidence (see second footnote) are compiled from, such as bibliographic databases, social media platforms, and Web sites. † A more inclusive/heterogeneous term used to account for the different types of evidence or data sources (e.g., quantitative and/or qualitative research, expert opinion, and policy documents) that may be eligible in a scoping review as opposed to only studies. This is not to be confused with information sources (see first footnote). ‡ The frameworks by Arksey and O'Malley (6) and Levac and colleagues (7) and the JBI guidance (4,5) refer to the process of data extraction in a scoping review as data charting. § The process of systematically examining research evidence to assess its validity, results, and relevance before using it to inform a decision. This term is used for items 12 and 19 instead of "risk of bias" (which is more applicable to systematic reviews of interventions) to include and acknowledge the various sources of evidence that may be used in a scoping review (e.g., quantitative and/or qualitative research, expert opinion, and policy document).