4. Discussion
infection, anxiety
INFECTION, DISEASES
This study was conducted when 57% of the eligible population in Hong Kong were fully vaccinated; however, the vaccination coverage was not enough to provide herd immunity to protect the entire population (In the survey experiment, loss-framing of information on vaccine effectiveness in terms of reducing risk of infection and mortality was found to be effective for increasing the willingness of those who received the vaccine to receive the vaccine earlier, which could improve the roll-out speed of vaccination coverage. The vaccine acceptance of those who did not receive the vaccine was higher when receiving loss-framing information, but the difference was not significant. As people tend to be more sensitive to losses than to gains of the same magnitude (The provision of a subsidized physician consultation could improve vaccine acceptance in both groups of people who received and did not receive the vaccine, which has rarely been tested as an intervention for promoting COVID-19 vaccination in previous research. Nevertheless, this finding is supported by several surveys that showed recommendation from doctors for vaccination play an important role in reducing vaccine hesitancy for vaccine against COVID-19 or other diseases (The third options tested in the survey was provision of cash incentives (HK$500/US$64), which had no effect on COVID-19 vaccine acceptance. This finding is different from both the outcomes of studies in the US and European countries that revealed cash incentives (ranging from US$24 to over US$50) could improve vaccine acceptance by 2–4% (Considering the findings, loss-framing of information and provision of subsidized physician consultation prior to vaccination could be helpful in promoting COVID-19 vaccination, particular for those with high perceived infection risk and severity of the condition, and unvaccinated people with concerns over vaccine safety. The findings on interactions between cues to actions and other HBM constructs indicate that it is important for clinicians and other public health professionals to understand individuals' perceptions on COVID-19 and the vaccine in practice, as it may influence the effect of different strategies for vaccination promotion. For use of loss-framing messages, individualized interventions should be considered in implementation rather than population-level dissemination of relevant messages, as loss-framing may induce powerless and fear in receivers, and cause anxiety among those who are more mentally vulnerable (This study possesses a few limitations. First, we recruited more people aged below 35 years and more females compared with the population in Hong Kong, which is why we adjusted for age and sex distribution in analysis for vaccine acceptance rate and its association with various factors. Second, we recruited both unvaccinated and vaccinated people to elicit their willingness to be vaccinated in the near future and earlier than they did in the past separately, so they were not combined for analysis because of the heterogeneous outcome measurements. By including vaccinated individuals, we aimed to find out whether relevant interventions can be used to accelerate their vaccination and increase vaccination roll-out speed—which is important in the evolving situation that characterizes epidemics. Meanwhile, the survey was conducted at a time when the third dose of vaccine was about to be made publicly available while there were no compulsory requirements or other incentives for people to accept the third dose. The acceptance rate of the vaccinated people can also be used to inform strategies to promote future booster dosage of COVID-19 vaccines. Nevertheless, the retrospective measurement of the latter group was not widely used in previous studies. There should be a larger sample of unvaccinated people recruited in future studies to find out the effect of these interventions amongst them.