Table 6.

The detailed key finding of included studies: country-wise.

Study ID	Country	Target population	Key findings
10, 12, 13, 15, 18, 19, 21	United States	General population	Association with higher vaccine acceptance: Gender(male), older adults, higher educational attainment, Healthcare providers would recommend vaccination, moderate or liberal in their political leaning, higher levels of perceived likelihood of getting a COVID-19 infection in the future, perceived severity of COVID-19 infection, perceived effectiveness of a COVID-19 vaccine, Cases, and mortality per million of a nation's population, history of COVID-19 infection, trust in government, high-income levels, employer's recommendation for vaccine, Vaccine efficacy, minor side effects, longer protection duration, high perceived benefits of the vaccine, income levels, vaccine history. Association with lower vaccine acceptance: Younger age (<60 years), Black race, lower educational attainment, and not having received the influenza vaccine in the prior year, low perceived risk, rural settings, unemployment, lower-income, no health insurance, conservative in their political leaning, higher level of perceived potential vaccine harms, Rushed vaccine development, Major side effects, vaccine low efficacy, Vaccine developed outside the United States, Political attributes (endorsement), whether FDA EUA approved. Concerns related to vaccine acceptance: Vaccine-specific concerns, a need for more information, anti-vaccine attitudes or beliefs, and a lack of trust.
5		Parents/caregivers	Association with higher vaccine acceptance: Older children, children with no chronic illness, children up-to-date on their vaccination schedule, the recent history of vaccination against influenza, and caregivers concerned their child had COVID-19 at the time of the survey. Association with lower vaccine acceptance: Mothers completing the survey, the child having a chronic illness. Concerns related to vaccine acceptance: Novelty, the perceived child is not at risk to contract COVID-19, side effects/safety concerns, efficacy concerns, general vaccine refusal, perceived contraindication, and may vaccinate if more information available/recommended by the healthcare provider.
8, 14, 15, 20	United Kingdom	General population	Association with higher vaccine acceptance: Gender(male), age Natural origin, Perceived risk of catching COVID-19, frequency of watching/listening/reading the news, higher COVID-19 anxiety, government satisfaction, higher education, Cases and mortality per million of a nation's population, history of COVID-19 infection, trust in government, high-income levels, employer's recommendation for the vaccine, Vaccine offered by the government, availability at the local pharmacy, keen attitude and eagerness to get vaccinated, taking the vaccine is important, encourages family and friends to get vaccinated. Association with lower vaccine acceptance: Potential side effects of the vaccine, against vaccination in general, religious reasons, Lower education, and income levels, Less following of all guidelines, less likelihood of taking a diagnostic test. Concerns related to vaccine acceptance: Potential side effects, the vaccine may not be safe, afraid of injections, believe natural, or traditional remedies, vaccine conspiracy beliefs.
11		Parents/caregivers	Association with higher vaccine acceptance: Household income. Association with lower vaccine acceptance: Ethnicity other than white, homemaker. Concerns related to vaccine acceptance: Vaccine safety and effectiveness, newness, and rapid development of the vaccine.
7		Vulnerable population (elderly/individuals with chronic respiratory disease)	Association with higher vaccine acceptance: Perception that COVID-19 will persist over time. Association with lower vaccine acceptance: Predicting that the media have exaggerated the risk. Facilitator of vaccine acceptance: Perceptions of risk to personal health, the severity of COVID-19, and health consequences to others. Concerns: Vaccine safety.
4, 15	China	General population	Association with higher vaccine acceptance: Age, gender (male), marriage status, risk perception, influenza vaccination history, the belief of COVID-19 vaccine efficacy, valuing doctor's recommendations, Higher levels of education, Cases, and mortality per million of a nation's population, history of COVID-19 infection, trust in government, high-income levels, employer's recommendation for the vaccine. Association with lower vaccine acceptance: Confirmed or suspected cases in local areas, valuing vaccination convenience or vaccine price, Lower education, and income levels.
1		Healthcare workers	Association with higher vaccine acceptance: Healthcare nurses in the private sector, nurses with chronic conditions, encountering suspected, or confirmed COVID-19 patients, and prior accepted influenza vaccination in 2019. Reasons for refusal and hesitation for COVID-19 vaccination: Suspicion on efficacy, effectiveness, and safety, believing it unnecessary, and no time to take the vaccine.
2, 6	Others	Healthcare workers	Association with higher vaccine acceptance: Self-perception of high-risk for severe COVID-19 infection, gender (male), influenza vaccination, Older age, fear about COVID-19. Association with lower vaccine acceptance: Having a child.
3, 8, 10, 14, 15, 16, 17, 22		General population	Association with higher vaccine acceptance: Age, Being a healthcare worker/occupation, married, higher perceived risk of COVID-19 infection, vaccine efficacy, gender(male), High perception of benefits, Natural origin, Perceived risk, of catching COVID-19, frequency of watching/listening/reading the news, higher COVID-19 anxiety, Higher levels of education, Cases and mortality per million of a nation's population, history of COVID-19 infection, trust in government and health system, high-income levels, employer's recommendation for the vaccine, health insurance, anxiety level, having children. Association with lower vaccine acceptance: Being Retired, Potential side effects of the vaccine, against vaccination in general, religious reasons, having children, Lower education and income levels, new vaccine, belief that COVID-19 infection is a biological weapon and the vaccine will serve those who produce this virus. Concerns related to vaccine acceptance: Afraid of injections believe natural or traditional remedies, Vaccine specific influences, time, and money willing to spend for vaccination.
5		Parents/caregivers	Association with higher vaccine acceptance: Older children, children with no chronic illness, children up-to-date on their vaccination schedule, the recent history of vaccination against influenza, and caregivers concerned their child had COVID-19 at the time of the survey. Association with lower vaccine acceptance: Mothers completing the survey, the child having a chronic illness. Concerns related to vaccine acceptance: Novelty, the perceived child is not at risk to contract COVID-19, side effects/safety concerns, efficacy concerns, general vaccine refusal, perceived contraindication, and may vaccinate if more information available/recommended by a healthcare provider.