Potential factors influencing COVID-19 vaccine acceptance and hesitancy: A systematic review
Authors: Roy Debendra Nath , Biswas Mohitosh , Islam Ekramul , Azam Md. Shah 
Published: March 2022

Background and aims
Although vaccines are considered the most effective and fundamental therapeutic tools for consistently preventing the COVID-19 disease, worldwide vaccine hesitancy has become a widespread public health issue for successful immunization. The aim of this review was to identify an up-to-date and concise assessment of potential factors influencing COVID-19 vaccine acceptance and refusal intention, and to outline the key message in order to organize these factors according to country count.

Methods
A systematic search of the peer-reviewed literature articles indexed in reputable databases, mainly Pub Med (MEDLINE), Elsevier, Science Direct, and Scopus, was performed between21stJune 2021 and10th July 2021. After obtaining the results via careful screening using a PRISMA flow diagram, 47 peer-reviewed articles met the inclusion criteria and formed the basic structure of the review.

Results
In total, 11 potential factors were identified, of which the greatest number of articles (n = 28) reported “safety” (34.46%; 95% CI 25.05─43.87) as the overarching consideration, while “side effects” (38.73%; 95% CI 28.14─49.32) was reported by 22 articles, which was the next common factor. Other potential factors such as “effectiveness” were identified in 19 articles (29.98%; 95% CI 17.09─41.67), followed by “trust” (n = 15 studies; 27.91%; 95% CI 17.1─38.73),“information sufficiency”(n = 12; 34.46%; 95% CI 35.87─63.07),“efficacy”(n = 8; 28.73%; 95% CI 9.72─47.74), “conspiracy beliefs” (n = 8; 14.30%; 95% CI 7.97─20.63),“social influence” (n = 6; 42.11%; 95% CI 14.01─70.21), “political roles” (n = 4; 16.75%; 95% CI 5.34─28.16), “vaccine mandated” (n = 4; 51.20%; 95% CI 20.25─82.15), and “fear and anxiety” (n = 3; 8.73%; 95% CI 0.59─18.05). The findings for country-specific influential vaccination factors revealed that, “safety” was recognized mostly (n = 14) in Asian continents (32.45%; 95% CI 19.60─45.31), followed by the United States (n = 6; 33.33%; 95% CI12.68─53.98). “Side effects” was identified from studies in Asia and Europe (n = 6; 35.78%; 95% CI 16.79─54.77 and 16.93%; 95% CI 4.70─28.08, respectively), followed by Africa (n = 4; 74.60%, 95% CI 58.08─91.11); however, public response to “effectiveness” was found in the greatest (n = 7) number of studies in Asian countries (44.84%; 95% CI 25─64.68), followed by the United States (n = 6; 16.68%, 95% CI 8.47─24.89). In Europe, “trust” (n = 5) appeared as a critical predictor (24.94%; 95% CI 2.32─47.56). “Information sufficiency” was identified mostly (n = 4) in articles from the United States (51.53%; 95% CI = 14.12─88.74), followed by Asia (n = 3; 40%; 95% CI 27.01─52.99). More concerns was observed relating to “efficacy” and “conspiracy beliefs” in Asian countries (n = 3; 27.03%; 95% CI 10.35─43.71 and 18.55%; 95% CI 8.67─28.43, respectively). The impact of “social influence” on making a rapid vaccination decision was high in Europe (n = 3; 23.85%, 95% CI -18.48─66.18), followed by the United States (n = 2; 74.85%). Finally, “political roles” and “vaccine-mandated” were important concerns in the United States.

Conclusions
The prevailing factors responsible for COVID-19 vaccine acceptance and hesitancy varied globally; however, the global COVID-19 vaccine acceptance relies on several common factors related to psychological and, societal aspect, and the vaccine itself. People would connect with informative and effective messaging that clarifies the safety, side effects, and effectiveness of prospective COVID-19 vaccines, which would foster vaccine confidence and encourage people to be vaccinated willingly.