Table 5.

Detailed key findings of the included studies according to the target population.

Study ID	Target population	Key findings
2, 3, 4, 8, 9, 10, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22	General population	Higher association of vaccine acceptance: Being a healthcare worker/occupation, higher perceived risk of COVID-19 infection, vaccine efficacy, gender (male), marriage status, influenza vaccination history, valuing doctor's recommendations, high perception of benefits, low perceived barriers to receiving the vaccine, higher educational attainment, moderate or liberal in their political leaning, belief in Natural origin of the infection, frequency of watching/listening/ reading the news, higher COVID-19 anxiety, government satisfaction, Age more than 25 years or older ages, Cases and mortality per million of a nation's population, history of COVID-19 infection, employer's recommendation for the vaccine, longer protection duration, having insurance, Vaccine offered by the government, availability at the local pharmacy, keen attitude, and eagerness to get vaccinated and length of vaccine testing. Lower association of vaccine hesitancy: Being Retired confirmed or suspected cases in local areas, valuing vaccination convenience or vaccine price, Potential side effects of the vaccine, against vaccination in general, and religious reasons, 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, no health insurance, conservative in their political leaning, Political attributes (endorsement), rushed vaccine development. Concerns related to vaccine acceptance: Potential side effects, the vaccine may not be safe, afraid of injections, believe natural or traditional remedies, need for more information, anti-vaccine attitudes or beliefs, and a lack of trust, the vaccine will serve those who produce this virus, Vaccine conspiracy beliefs.
1, 2, 6	Healthcare workers	Higher association of vaccine acceptance: Healthcare nurses in the private sector, nurses with chronic conditions, encountering with suspected or confirmed COVID-19 patients, and prior accepted influenza vaccination in 2019, self-perception of high-risk for severe COVID-19 infection, gender (male), Older age. Lower association of vaccine acceptance: Suspicion on efficacy, effectiveness, and safety, believing it unnecessary, and no time to take the vaccine, having a child. Concerns related to vaccine acceptance: Quality control, potential side effects, and associated COVID-19 illness.
5, 11	Parents/caregivers/guardians	Higher association of vaccine acceptance: Older children, children with no chronic illness, children up-to-date on their vaccination schedule, household Income, the recent history of vaccination against influenza, and caregivers concerned their child had COVID-19 at the time of the survey. Lower association of vaccine acceptance: Mothers completing the survey, Child having a chronic illness, ethnicity other than a white, homemaker. 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, newness and rapid development of the vaccine.
7	Vulnerable population (elderly/individuals with chronic respiratory disease)	Higher association of vaccine acceptance: Perception that COVID-19 will persist over time. Lower association of 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.