A cross-sectional study was conducted at Bule Hora University Teaching Hospital in West Guji Zone, Oromia, south Ethiopia from April 10 to May 30, 2022. It is 467 km from Addis Ababa. The hospital served around 1,568,547 people and employed 408 staff (117 administrative and 233 clinical staff). In the year 2021, about 3,528 patients will be served in the outpatient service at Bule Hora Teaching Hospital.

Inpatient services at Bule Hora University Teaching Hospital include obstetric, gynaecologic, and neonatal intensive care units, as well as medical and surgical wards. Outpatient services include ANC, postnatal care, ART clinic, PMTCT, family planning, ophthalmology care, psychiatry, dental care, cervical cancer screening, under-5 OPD, emergency OPD, and adult OPD's. Additional services include laboratory and pharmaceutical services, as well as US and x-ray services.

All clients aged ≥18 years attending Bule Hora University Teaching Hospital were the source population while all randomly selected clients aged ≥18 years and attending Bule Hora University Teaching Hospital during data collection time were the study population. Those clients who had been vaccinated were excluded.

The sample size for the first objective was calculated by using a single population proportion formula considering 59.4% (26) proportion of willingness to receive the COVID-19 vaccine from previous study, with assumptions of confidence level at 95%, a margin of error (d) 5% and adding 10% for non-response as follows:

The sample size for the second specific objective was determined by considering factors that were significantly associated with the outcome variable, two-sided confidence level of 95%, the margin of error of 5%, power of 80% and the ratio of exposed to unexposed 1:1 using EPI-Info software. Considering 10% for nonresponse the final sample size for the second objective was determined. Hence, the largest sample size was taken from first objective, 385.

Six outpatient departments were chosen from the total departments in the hospital using a simple random sampling technique by lottery method. A systematic random sampling procedure was used to choose clients from these six outpatient departments; the first client was selected using a simple random sampling technique, and the others were selected at 9 regular intervals until the required sample size was reached.

The data were collected through interviews and observations using a pre-tested structured questionnaire, which was adapted from published papers (16, 25–27). It consists of four sections including socio-demographic characteristics, knowledge about the COVID-19 vaccine, attitude towards the COVID-19 vaccine, adherence toward COVID-19 mitigation measures, and willingness to receive the COVID-19 vaccine. Prior to data collection, two days of training was given for data collectors and supervisors on the study objectives, subject eligibility criteria and data collection methods. The data was collected by 6 BSc nurses and supervised by 2 BSc nurses.

Willingness: a state of being prepared or readiness to receive the COVID-19 vaccine. COVID-19 vaccine acceptance was measured using a “Yes” and “No” question: the participant was asked “Are you willing to be vaccinated against COVID-19?” (26).

Knowledge: Eight items were used to assess the knowledge level of the client about the COVID-19 vaccine. Those who correctly answered the question were coded as ″1″, while incorrect answers were given ″0″ values. Participants who scored 70% and above were considered as having good knowledge while those who scored less than 70% were considered as having poor knowledge towards the COVID-19 vaccine (26).

Adherence towards COVID-19 mitigation measures: a composite variable generated from hand washing, using a facemask, keeping physical distance, not travelling to a crowded place, staying at home, and not travelling to any place out of the city in the last 14 days. Hence, an individual was considered as having good adherence towards COVID-19 mitigation measures if they were able to answer “yes” to the median and above of the aforementioned composite variables (28).

Attitude: a settled way of thinking or point-of-view about the COVID-19 vaccine of patients attending the hospital was assessed by assigning one point for each correct answer. The attitude level indicated by the Likert scale: clients who strongly agree, 5 points; agree, 4 points; neutral, 3 points; disagree, 2 points; and strongly disagree, 1 point for positive question and vice versa for negative one. The respondent attitude ranged from 1 to 25 and a cutoff point greater than equal ≥44% (11–25) was considered as a favorable attitude while less <40% were taken as unfavorable attitude toward the COVID-19 vaccine (26).

To ensure data quality, a pre-test was conducted among 5% of the sample size in Yabello General Hospital to ensure the validation of the tool. Amendments were made based on the feedback of the pre-test before the commencement of the final data collection. Two days training was given for the data collectors and supervisors on the aim of the study, clarity of the measuring tool, and ethical considerations. The quality of the data was monitored frequently in the field through close supervision of data collectors.

The coded data were entered in to EpiData software version 3.1 and it was exported to SPSS version 25 for further analysis. Descriptive statistics were computed to describe sample population characteristics relevant to the variables. Logistic regression was fitted to identify factors associated with willingness to accept the COVID-19 vaccine. The analysis was conducted to select candidate variables for the multivariable model. Those variables that show association with willingness at a p-value less than 0.25 were included in the multivariable logistic regression model. Both crude and adjusted odds ratios with their corresponding 95% confidence interval were used to determine the strength of association. Multicollinearity was checked by using VIF to find correlations between independent variables; no variables with VIF >10 were observed. The model goodness of fit was tested by the Hosmer and Lemeshow statistical test; the model was considered a good fit since it was found to be non-significant for Hosmer and Lemeshow (P = 0.651). Statistical significance was declared at p-value < 0.05.

This study included 385 participants, with a 100% response rate. There were 207 (53.8%) females participants and 215 (55.8%) participants were married. Two hundred fifty (63%) of the participants are between the ages of 18 and 35, with a median age of 30 years. One hundred twenty nine (33.5%) of the respondents had completed secondary education and above. The majority [267 (69.4%)] of participants lived in urban areas; 309 (80.3%) were Oromo by ethnicity; 33.8% worked for the government; and 229 (59.5%) had monthly incomes of at least 4,000 Ethiopian Birr (ETB) (Table 1).

Of the 385 study participants, 86 (22.3%) were still of the view that COVID-19 does not exist in Ethiopia. 295 (76.6%) of them were unaware that the vaccine must be administered twice during a 28-day period. In total, 179 (46.5%) of the participants were well-informed about the COVID-19 vaccination (Table 2).

Of the respondents, 190 (49.4%) disagree that COVID-19 is a minor disease that does not necessitate vaccination. Yet, 122 (31.7%) of the participants strongly believe that taking additional precautionary measures is far superior to receiving the COVID-19 vaccine. On the other hand, 60 (15.6%) of participants strongly agree that the negative effects of the COVID-19 vaccine outweigh the vaccination benefit, and 43 (11.2%) of respondents strongly agree that being infected with COVID-19 disease is preferable to receiving the vaccine. Overall, 272 (70.6%) of respondents were had a positive attitude towards the COVID-19 vaccine (Table 3).

Of 385 participants, 62.6% did not stay at home when they experienced flu-like symptoms. The majority of participants, 289 (75.1%), covered their mouth during sneezing or coughing. When they arrive for service, approximately 68.6% of respondents wear a face mask. Overall, 215 (55.8%) of the clients adhered to the COVID-19 mitigation measures (Table 4).

According to the findings of this study, nearly 260 (67.5%) (95% Cl: 63–72) of the participants were willing to accept the COVID-19 vaccine if it was provided for free (Figure 1).

Bivariable analysis was performed using odds ratio at 95% confidence interval and variables with P- value of < 0.25 in bivariable analysis were considered as candidates for multivariable logistics regression. The result of bivariable logistic analysis shows that residence, age, occupation, chronic illness, knowledge, attitude and adherence were factors associated with willingness to accept the COVID-19 vaccine. In multivariable analysis the occupation, chronic illness, knowledge, attitude, and level of adherence to mitigation measures of the respondents were associated with willingness to accept the COVID-19 vaccine. Government employee were 2 fold more likely willing to accept the COVID-19 vaccine compared to (AOR = 2.35; 95% Cl: 1.1–5.0) their counterparts.

Clients with a history of chronic diseases were 2.59 times more likely to be willing to accept the COVID-19 vaccine (AOR = 2.59:95% Cl: 1.4–4.78) compared to those without a history of chronic illness.

Those clients with good knowledge were 2 times more likely to be willing to accept the COVID-19 vaccine (AOR = 2.07; 95% Cl: 1.17–3.64) than those with poor knowledge. Clients with favorable attitudes towards the COVID-19 vaccine were 14 times more likely to accept the vaccine (AOR = 14.15; 95% Cl: 5.25–37.46) compared to clients with unfavorable attitudes. Those clients with good adherence were 1.74 times more likely to accept the COVID-19 vaccine with (AOR = 1.74; 95%; Cl; 1.02–2.97) when compared to those with poor adherence (Table 5).

This study focuses on COVID-19 vaccine acceptability and associated factors, which will be useful for decision makers, policy designers, implementers, and managers of health care organizations at all levels to enhance vaccination uptake.

Since only Johnson & Johnson and AstraZeneca provided the COVID-19 vaccine at the study site, the age limit has been set at 18 years and above. But, when data collecting was completed, other vaccines, such as Pfizer, were administered to clients aged 12 and up. It would be preferable if clients aged 12 and up were included in the research. Furthermore, due to the nature of the study design, causal inference may not be inferred from this study.