Discussion

In the present study, we investigated the intention of free or self-paid SARS-CoV-2 vaccination and the associated factors based on the SCT among HCWs in China. Overall, 68% of the doctors and 75% of the nurses intended to take up free SARS-CoV-2 vaccination. However, the prevalence dropped to 57% and 65% at a fee of 600 RMB ($US91), corroborating previous studies among Chinese university students and general population in Hong Kong. ^{Reference Mo, Luo and Wang16,Reference Yu, Lau, Lau, Wong and Chan17} Cost is an expected barrier, and the concerns about downturns in economy due to the pandemic may have further reduced the willingness to pay. Free and prioritized SARS-CoV-2 vaccination should be provided to these vulnerable occupational groups to avoid nosocomial infections during the pandemic. Although a prior study suggested that a coverage rate of ≥75% would be required to achieve herd immunity with a 80% vaccine effectiveness, ^{Reference Bartsch, O’Shea and Ferguson18} the intention–behavior gap signifies the necessity of continuous efforts to promote vaccination uptake. Corroborating a previous Israel study, ^{Reference Dror, Eisenbach and Taiber5} doctors indicated higher SARS-CoV-2 vaccination intention than nurses. Future studies should investigate the reasons behind the discrepancy in motivation for SARS-CoV-2 vaccination between these 2 groups. Additional efforts and incentives should be given to promote SARS-CoV-2 vaccination among HCWs, especially for nurses.

The SCT is applicable to understanding the intention to take a SARS-CoV-2 vaccination among HCWs. Most of the SCT factors (outcome expectations, self-efficacy, norms, and COVID-19–related work experience) were significantly and consistently associated with both free and self-paid vaccination intentions among the 2 groups. Observational learning was an exception and was not associated with vaccination intentions. This finding is understandable because SARS-CoV-2 vaccination had not been implemented, although a very small number of HCWs might have taken up experimental vaccinations. ^{Reference Zhu, Guan and Li19} Thus, observational learning, which involves information processing and responses, ^{Reference Bandura8} might not have occurred among most participants. The significance of this potential factor of SARS-CoV-2 vaccination would evolve over time.

Supporting the SCT, outcome expectations were significant factors of SARS-CoV-2 vaccination intention among HCWs. Corroborating a previous study, ^{Reference Bandura8} perceived protectiveness of COVID-19 vaccination (oneself and family or friends) was significantly associated with all vaccination intention variables. Thus, SARS-CoV-2 vaccination health promotion may highlight both egoistic and altruistic benefits. Unexpectedly, perceived side effect of vaccines was not associated with vaccination intention in the present study. It was, however, negatively associated with various types of vaccination-related behaviors or intentions (eg, influenza) in previous studies. ^{Reference Sherman, Smith and Sim20,Reference Bish, Yardley, Nicoll and Michie21} It is plausible that side effects were rarely reported during the experimental use of the Chinese SARS-CoV-2 vaccines. In addition, the item about free or self-paid COVID-19 intention specifically referred to vaccines with rare mild side effects. Thus, participants’ responses to such questions did not involve consideration of perceived side effects of SARS-CoV-2 vaccines. Future studies need to confirm and explain this unexpected finding. Furthermore, self-evaluative outcome expectations of positive feelings and anticipated regret about SARS-CoV-2 vaccination were also significantly associated with vaccination intentions. These findings suggest that psychological outcomes such as peace of mind by avoiding regret and positive feelings resulted from SARS-CoV-2 vaccination are potential themes for related health promotion.

As expected, self-efficacy was associated with SARS-CoV-2 vaccination intentions. It is a key construct of a number of behavioral theories (eg, the Health Belief Model and Theory of Planned Behaviors) and has been shown to be a significant determinant of multiple types of behaviors and intentions regarding vaccination, including influenza and COVID-19 vaccination. ^{Reference Ng, Cowling, So, Ip and Liao12,Reference Godin, Vézina-Im and Naccache13,Reference Sherman, Smith and Sim20} Evidence based on workplace vaccination programs suggest that vaccines may be offered on-site and provided free, at multiple locations, on multiple shifts or days, with health education and mobile units for information dissemination to reduce logistics barriers and increase availability and self-efficacy of vaccination for HCWs. ²² Doctors showed higher self-efficacy of SARS-CoV-2 vaccination (eg, confidence in getting the quota and time) than nurses, which might partially explain the higher vaccination intention among doctors than nurses. Our data also supported this speculation (not shown). In general, doctors are more likely than nurses to possess higher positions in the hierarchy of power and decision making. ^{Reference Elsous, Radwan and Mohsen23} Nurses should be assured about their priority to take up SARS-CoV-2 vaccination as a means to increase self-efficacy.

A novel feature of this study is that following the SCT, it has considered various types of descriptive, subjective, moral, and professional norms and work experiences as part of the environmental and contextual factors. All 4 types of norms were consistently and positively associated with vaccination intentions among doctors and nurses, corroborating prior studies about influenza vaccination behaviors of HCWs. ^{Reference Ng, Cowling, So, Ip and Liao12,Reference Godin, Vézina-Im and Naccache13} In general, literature shows that social norms can be fostered to result in behavioral changes, ^{Reference Miller and Prentice24} and such findings could be considered in relevant health promotion campaigns for SARS-CoV-2 vaccination. First, future intervention should consider peer sharing sessions, newsletters, declarations of professional societies through existing online platforms used by HCWs to build up professional and descriptive norms regarding SARS-CoV-2 vaccination among HCWs. Second, our findings indicate that SARS-CoV-2 vaccination might be seen as a moral and prosocial behavior related to others’ health. Such positive framing of SARS-CoV-2 vaccination as a prosocial behavior could be a feasible marketing approach to promote SARS-CoV-2 vaccination. ^{Reference French, Blair-Stevens, McVey and Merritt25} Third, the present study showed that subjective norms perceived from peers, general public, hospital, government, and social media were significantly associated with SARS-CoV-2 vaccination intentions. Thus, health planners should regard SARS-CoV-2 vaccination both as an individual and social behaviors, and social media might be a feasible approach for health promotion.

As another dimension of environmental influence, engagement in the COVID-19 treatment and care was positively correlated with self-paid vaccination intention among doctors, corroborating a previous study. ^{Reference Dror, Eisenbach and Taiber5} Such experiences may be associated with perceived susceptibility, which was usually associated with vaccination behaviors. ^{Reference Wong, Alias, Wong, Lee and AbuBakar26} With regard to free vaccination, it is possible that HCWs who were not involved in COVID-19 work also showed relatively high willingness for SARS-CoV-2 vaccination due to no cost, which might explain the nonsignificant association. Furthermore, no significant associations between COVID-19–related work and vaccination intentions among nurses were observed. A previous study among nurses suggested that COVID-19–related work was positively associated with SARS-CoV-2 vaccination intention via increased work stress. ^{Reference Kwok, Li, Wei, Tang, Wong and Lee27} It is plausible that nurses in mainland China who had not been involved in COVID-19 work were also experiencing greater work stress during the pandemic. Empirical data are needed to substantiate these propositions. Interestingly and importantly, job satisfaction was positively associated with vaccination intentions, corroborating previous studies for influenza vaccination. ^{Reference Naleway, Henkle and Ball28} Job satisfaction has been associated with lower turnover intention and higher organizational commitment among HCWs ^{Reference Delobelle, Rawlinson, Ntuli, Malatsi, Decock and Depoorter29} ; therefore, HCWs with higher levels of job satisfaction may be more likely to conform to expected behaviors for HCWs (eg, vaccination). This finding reinforces the importance of environmental interactions with preventive behaviors, as highlighted by the concept of reciprocal determinism of the SCT. This is particularly crucial because many HCWs are fighting against COVID-19 in risky, stressful, and less rewarding working environments. ^{Reference Liu, Luo and Haase30} The finding sends a reminder to policy makers that HCW vaccination compliance may be based on their job satisfaction and environment.

This study has several limitations. Reporting bias may have occurred due to social desirability associated with SARS-CoV-2 vaccination. The cross-sectional study design cannot allow for making causal inferences; longitudinal studies are warranted. Despite a high response rate, only 5 tertiary-care hospitals in 3 provinces of China were involved. The generalization of these results to hospitals of other levels or provinces should be done with caution. The gender distribution was comparable to the census data for doctors (male: 54.9% vs 51.7%) and nurses in 2018 (male: 2.2% vs 3.3%). ³¹ However, the sample was overrepresented by HCWs with higher educational levels because we focused on HCWs in tertiary-care hospitals. The prevalence of SARS-CoV-2 vaccination might be overestimated; education was positively associated with vaccination behavior among HCWs. ^{Reference Maltezou, Theodoridou, Ledda, Rapisarda and Theodoridou32} The sample sizes of the 2 groups were uneven and implied lower statistical power in the doctor group, making comparisons of the significance of factors difficult. In the absence of existing tools in the context of SARS-CoV-2 vaccination, some measurements were constructed for this study and referred to previous studies (eg, positive feelings associated with SARS-CoV-2 vaccination). In the present study, we considered the intention to be vaccinated because actual SARS-CoV-2 vaccination had not yet become available, and there is always a discrepancy between intention and action. Future studies are required to compare such differences and validate the present findings. Last, we did not include other types of HCWs because we wanted to keep the sample as homogeneous as possible.

In summary, in the present study, ˜70% of HCWs had behavioral intention to take a free SARS-CoV-2 vaccination with 80% effectiveness and rare mild side effect. This rate dropped to 60% a fee of 600 RMB (US$91) was applied. A number of SCT constructs were associated with SARS-CoV-2 vaccination intention. Prompt theory-driven social marketing is warranted to improve the coverage of SARS-CoV-2 vaccination among HCWs. Future longitudinal studies and randomized controlled trials should be implemented to test the applicability of SCT and whether outcome expectations, norms, self-efficacy, and work environment would increase vaccination uptake. Other evidence-based interventions, such as facilitating vaccination behavior through reminders and prompts and reducing barriers through logistics and healthy defaults (eg, no cost, worksite vaccination, and availability), could also be considered in vaccination health campaigns. ^{Reference Brewer, Chapman, Rothman, Leask and Kempe33}