This study was reported following the Strengthening the Reporting of Observational Studies in Epidemiology (25). An online cross-sectional questionnaire-based survey was performed between 15th of November 2021 and 7th January 2022, involving Greek-Cypriot HCPs working in either public or private service provision, aged 18 years old and above, and living in the five government-controlled municipalities of the Republic of Cyprus (Nicosia, Limassol, Larnaca, Paphos, and Ammochostos). The online questionnaire was administered using Google Forms and dispersed using instant messaging apps (e.g., WhatsApp, Viber), social media platforms (e.g., Facebook, Instagram), and social networking sites (e.g., LinkedIn). Due to the quarantine restrictions resulting from the ongoing COVID-19 pandemic, a nonprobability convenience sampling approach was used to recruit participants. The required sample size to estimate the percentage of HCPs who support mandatory COVID-19 vaccination using a 95% confidence interval (CI) with a precision of 5%, assuming a true percentage of 35–95% was n = 139–350.

The online questionnaire included 47 open-ended and closed-ended questions in the Greek language about sociodemographic characteristics (e.g., age, gender, educational level, marital status, annual income), health-related status (e.g., presence of chronic diseases), information about their trust and attitudes toward healthcare system, satisfaction with it, as well as use of preventive healthcare services, information about COVID-19 vaccination (e.g., vaccination status, number of doses, type of COVID-19 vaccine, intention to receive another dose if requested etc.), sources of vaccine-related information (e.g., internet/social media, TV/newspapers/radio, scientific journals, personal doctor, colleagues/friends/family etc.), information about the reasons for vaccination refusal (e.g., fear of adverse side effects, expedited development and approval of the vaccine, concerns about getting infected from the vaccine etc.), participants' general vaccine knowledge, and attitudes toward mandatory COVID-19 vaccination. Questions about personal freedoms, human rights, and ethical aspects of mandatory COVID-19 vaccination were used, to reflect the overall attitudes of participants toward such policy. The questionnaire was developed by our research team, based on our previous research experience and extensive literature search (26–32). Validity assessment was done in a pilot study of 50 participants before to the actual study. To achieve a high level of face validity we assess the clarity and application of all survey items, as well as to address wording issues. Specific words were eliminated or replaced based on participants' suggestions to heighten participants' understanding. Internal consistency of the study instrument was assessed with Cronbach's alpha coefficient ranged between 0.63 and 0.96, suggesting acceptable internal consistency. The pilot sample was not included in the study sample.

This study was carried out following the Helsinki Declaration guidelines and was approved by the Cyprus National Bioethics Committee (CNBC) (EEBK E⊓ 2021.01.219). Participation was anonymous, and all participants were informed about study purpose and objectives before taking part. Participants gave their consent before completing the questionnaire by answering a “Yes/No” question on a mandatory electronic form.

The Shapiro-Wilk normality test was used to examine the normality of the continuous variables. Participants' characteristics are presented as mean ± standard deviation (SD) for continuous measures with normal distribution and absolute (n) and relative (%) frequencies for categorical variables. To assess the association between mandatory COVID-19 vaccination and the categorical characteristics, the chi-square test of independence was used. The Student's t-test was used for the comparison of mandatory COVID-19 vaccination and continuous baseline participant characteristics with normal distribution.

Participants' vaccination knowledge was measured using a 12-item scale. A vaccination knowledge score was created for each participant by scoring the individual knowledge question items, giving a score of 1 for each question correctly answered and 0 for each question answered incorrectly or in “I do not know” responses. The knowledge score was calculated by adding the points of each of the 12 knowledge items (maximum score 12). The tertiles of vaccination knowledge score were defined as follows: low vaccination knowledge (score ≤ 8), moderate vaccination knowledge (score 8.1–9), and high vaccination knowledge (score ≥ 10). Higher scores indicate a higher vaccination knowledge.

Hierarchical logistic regression analysis was used to examine the association between sociodemographic characteristics (Model 1) and vaccination knowledge score (Model 2) on mandatory vaccination support (Yes vs. No). Firstly, we added the sociodemographic characteristics as independent variables in a model including mandatory vaccination support as the dependent variable. Then, we added the vaccination knowledge score. Radar graphs were constructed to present the reasons for vaccination and the reasons for hesitating to get vaccinated against COVID-19. All statistical tests performed were two-sided with the statistical significance level set at α = 0.05. Statistical analysis was conducted using STATA 14.0 (Stata Corp, College Station, TX, USA) and Microsoft Excel 2013.

There was a total of 504 HCPs participated in the study among whom 223 (48%) were nursing staff, 76 (16.3%) were pharmacists, 73 (15.7%) were physicians, 62 (13.3%) were other Non-medical professionals (i.e., laboratory workers, nutritionists, occupational therapists, psychologists, radiologists, speech and language therapists, care assistants, and administrative personnel) and 31 (6.7%) were physiotherapists (Table 1). The mean age of the respondents was 36.7 years old (SD = 9.6). The majority of HCPs were female (n = 320, 63.5%) and residents of the capital of Cyprus, Nicosia (n = 232, 46.0%). More information about the sociodemographic characteristics is presented in Table 1.

Among the HCPs, 172 (34.4%) were in favor of mandatory COVID-19 vaccination, and 328 (65.6%) were opposed to such a policy. The mean age of those who did not support the mandatory vaccination was 34.9 ± 8.9 years, and for those who support it was 40.1 ± 10.1 years (p < 0.001) (Table 1). Most of the residents of all geographical areas were against the mandatory COVID-19 vaccination (p = 0.001), while the majority of supporters were physicians (n = 39, 53.4%) and other Non-medical professionals (n = 27, 43.6%) (p = 0.002) (Table 1).

Although we did not find a statistically significant association between gender and HCPs' perspectives toward mandatory COVID-19 vaccination (p = 0.440), we identify statistically significant associations among other sociodemographic characteristics that are presented in Table 1. Among those, the largest differences were observed in unmarried individuals (80.8% vs. 19.2%, for no and yes, respectively) (p < 0.001), and those who completed an undergraduate education (70.2% vs. 29.8%, for no and yes, respectively) (p = 0.025).

Information about HCPs' health status and their attitudes toward healthcare services was retrieved through the survey, with around 20% of HCPs reporting at least one chronic disease. Most of the participants declared the moderate usage of preventive healthcare services (n = 183, 36.6%) and had a strong trust in the official guidelines and recommendations of the national healthcare authorities (n = 179, 35.7%). Approximately half of the HCPs were moderately satisfied with the healthcare system (n = 12, 85.7%), and they follow doctor's instructions very often (n = 67, 47.2%). In addition, most of the participants believe that the vaccine helped them to prevent COVID-19 disease a lot (n = 144, 38.0%) (Supplementary Table 1). Statistically significant differences between trust in official guidelines and recommendations by the national healthcare authorities, satisfaction with the healthcare system, following doctor's instructions/medical adherence, and mandatory vaccination support groups were identified (p < 0.001). Specifically, the largest percentage of participants who support the mandatory COVID-19 vaccination have a very strong trust in the official guidelines and recommendations of the national healthcare authorities (n = 59, 77.6%), they are extremely satisfied with the healthcare system (n = 12, 85.7%), and they follow doctor's instructions very often (n = 67, 47.2%). In addition, most of the participants believe that the vaccine helped them to prevent COVID-19 disease a lot (n = 144, 38.0%) (Supplementary Table 1).

A considerably high proportion of HCPs were vaccinated against COVID-19 (n = 350, 70.4%), with two doses (n = 179, 50.7%) of the Pfizer vaccine (n = 236, 66.7%) (Supplementary Table 2). The primary reasons for vaccination were to protect themselves (29.3%), their families (28.5%), and others (26.0%) (Supplementary Figure 1), while common reasons for vaccine refusal were the expedited development and approval of the vaccine (26.5%), fear of adverse side effects/safety concerns (25.0%), and preference for natural immunity (17.7%) (Supplementary Figure 2). HCPs retrieved information about the COVID-19 vaccination from scientific journals (24.8%), internet/social media (24.7%), and TV/Newspapers/Radio (14.5%) (Supplementary Figure 3). In addition, we found statistically significant associations between HCPs' COVID-19 vaccination status and mandatory vaccination support groups, which are presented in Supplementary Table 2.

Regarding HCPs' attitudes toward mandatory COVID-19 vaccination, many participants strongly disagree with COVID-19 vaccination mandate (n = 200, 39.8%), and that mandatory disposal of COVID-19 vaccines is ethically and scientifically justified (n = 160, 31.8%) (Table 2). Additionally, most of the respondents strongly disagree that mandatory COVID-19 vaccination is a policy that will reinforce their understanding that (i) the COVID-19 vaccine is necessary (n = 161, 32.3%), (ii) vaccine side effects are rare (n = 160, 32.2%), (iii) the vaccine has been studied well (n = 163, 32.6%). Approximately one-third of participants strongly agree that mandatory COVID-19 vaccination of HCPs is a policy directed against individual freedoms (n = 170, 33.9%) and violates human rights (n = 184, 36.7%). Most of the participants strongly agree that COVID-19 vaccination should be mandatory for HCPs (e.g., doctors, nurses, etc.) (n = 160, 31.8%). Interestingly, none of the HCPs who disagree or strongly disagree that COVID-19 vaccination should be mandatory for HCPs, support mandatory vaccination, while the corresponding percentages among those who neither agree nor disagree, agree, and strongly agree with that attitude were 10.3, 34.9, and 85.0%, respectively (p < 0.001). Finally, we observed statistically significant associations for all the attitudes toward mandatory COVID-19 vaccination among mandatory vaccination support groups (p < 0.001) (Table 2).

The mean vaccination knowledge score was 8.6 which indicates a sufficient vaccination knowledge (Table 3). We found a statistically significant difference in the mean vaccination knowledge score among mandatory COVID-19 vaccination groups (p < 0.001). Specifically, we reported a higher mean vaccination knowledge score among those who support mandatory COVID-19 vaccination (9.5) compared to those who did not support mandatory COVID-19 vaccination (8.1). Also, we found a statistically significant association between vaccination knowledge level and mandatory COVID-19 vaccination groups (p < 0.001). Most of the participants who support mandatory COVID-19 vaccination were among those with a high vaccination knowledge level (n = 101, 52.6%), followed by those with a moderate vaccination knowledge level (n = 33, 29.7%), and those with a low vaccination knowledge level (n = 38, 19.3%). More information regarding vaccination knowledge items overall and by mandatory vaccination support are presented in Supplementary Table 3.

Hierarchical logistic regression models for sociodemographic and vaccination knowledge scores on mandatory vaccination support were applied (Table 4). Firstly, we applied a model adding various sociodemographic characteristics (Model 1). We found that increased age was associated with a higher probability of supporting the COVID-19 mandatory vaccination (OR: 1.03, 95% CI: 1.01–1.06). Moreover, we revealed that nursing staff had 49% (95% CI: 0.28–0.93) lower probability of supporting mandatory vaccination compared to physicians. When we added vaccination knowledge score in the model (Model 2), we found that only the association for age (OR: 1.03, 95% CI: 1.01–1.06) with COVID-19 mandatory vaccination remained statistically significant. Divorced/separated/widowed individuals had 3.19 times higher probability of supporting the mandatory vaccination compared to married/in cohabitation respondents (95% CI: 1.18–8.62). We also reported that as vaccination knowledge score increases, the probability of supporting mandatory COVID-19 vaccination increases by 1.55 times (95% CI: 1.33–1.81).