Coronavirus (COVID-19) vaccine barriers and incentives to uptake: literature review

Complacency

As illustrated above, complacency results from a consideration of vaccines as unnecessary due to one's perception of being at low risk of catching Covid-19 or experiencing severe disease outcomes. The underestimation of the consequences deriving from infection relates both to lack of knowledge or misconceptions about Covid-19, and to the absence in one's social network of people who have become severely ill with the virus.

Levels of complacency have varied over time and have been influenced not only by personal and social factors, but also by the number of cases and emerging science. For instance, a rise in vaccine hesitancy has usually coincided with the easing of Covid-19 restrictions, likely associated with the belief that the virus was under control and there was low risk of getting infected. Some have also suggested that the awareness that Covid-19 disproportionally impacts older people and those with pre-existing conditions may have played a role in determining low vaccine uptake in younger cohorts^[43]. Furthermore, while new waves have usually led to an increase in vaccine acceptance as perception of risk heightened^[44], more recently the new findings on the Omicron variant and the milder disease severity it causes seem to have negatively affected uptake^[45]. In January 2022, data from the Scottish Government YouGov polling revealed that 29% of those who were given at least one dose but were unlikely to receive a further one mentioned their perception of being at low risk as a reason, with 36% of the total sample saying they were concerned the vaccines would not work against the new strain^[46].

There are a number of studies which have explored the ways in which risk perception is intertwined with vaccine acceptance. For example, a cross-sectional analysis of the results from the Covid-19 Psychological Wellbeing Study from April/May 2020 shows that perceiving oneself to be at low risk of infection in the coming 6 months was associated with vaccine hesitancy among key workers, while not knowing someone diagnosed with Covid-19 was a factor among non-key workers^[47]. Moreover, a mixed method study exploring attitudes towards Covid-19 vaccines reports that in December 2020 there was a perception of being at low risk among those planning to refuse the offer of any dose^[48]. Similarly, a survey administered to a nationally representative sample in December 2020 found that those who did not consider Covid-19 a threat were two and a half times less likely to accept a vaccine^[49], while a poll by IPSOS administered in May 2021 revealed that 24% of the sampled population thought Covid-19 was unlikely to make people seriously unwell^[50]. Finally, the large scale prospective longitudinal COPE study, which explored the UK population's experiences of the pandemic, confirms that low fear of the disease is a key factor in vaccine refusal. Follow-up data at 12 months from the initial recruitment show an increase in perceived low susceptibility to Covid-19 and perceived personal control over reducing the threat. This has been explained by the researchers with a combination of factors, such as people adjusting to the pandemic context and immunisation due to the vaccines or natural exposure to the virus^[51].

Indeed, the belief that vaccination could be avoided by relying on one's immune system or on the diligent adoption of protective measures is a recurrent theme. Data from the UK-REACH prospective cohort study referring to the period December 2020 - February 2021 show that clinical and non-clinical health care workers were more likely to be vaccine hesitant if they had had Covid in the past, suggesting a belief that natural infection guarantees sufficient immunological protection^[52]. A cross-sectional study conducted at the University Hospitals of Leicester NHS Trust attributed the finding that those with a history of Covid-19 infection were less likely to be vaccinated to the same belief. The research also concluded that the likelihood of getting vaccinated was lower in younger healthcare workers not only because older colleagues had had more time and opportunity to receive their dose (due to the priority groups established in the vaccination programme), but also because of a reduced perception of personal risk of severe disease^[53]. Qualitative data from the Tackling Inequalities and Discrimination Experiences in health Services (TIDES) study carried out between October 2020 and January 2021 confirmed these points: in depth-interviews with healthcare staff revealed how decision-making revolved around an evaluation of risks from the vaccines and from natural infection, with some participants questioning the necessity of vaccination if one was generally healthy or had already had Covid-19^[54].

Data on specific groups and risk perception are also available. Qualitative work with pregnant women interviewed in April/May 2020 in the Bristol area shows how most participants perceived the vaccine as riskier than the infection itself^[55]. Research conducted in the few months before vaccine deployment also highlighted how smokers were more likely to decline any dose compared to non-smokers^{[56] [57]}. While this could be explained by the fact that smokers are generally less risk adverse compared to the general population, some scholars suggested that decision making may have been impacted by the circulation of debatable evidence on smokers being 30% less likely to become infected with the virus^[58]. Finally, a cross-sectional survey administered in April 2020 found that older adults and those who suffer from chronic respiratory diseases are less likely to be vaccine hesitant due to their perception of being at high risk if they caught Covid-19^[59].

Findings on those affected by mental health conditions are conflicting. One study highlights how depression and anxiety are associated with a lower prevalence of health protective-behaviours (e.g. in relation to smoking, exercise or diet) and that individuals experiencing these conditions are usually more likely to be vaccine hesitant^[60]. On the other hand, findings from the OxWell Student Survey administered in England illustrate a correlation between hesitancy and lower levels of anxiety and depression in students aged 12+^[61]. Therefore, some scholars have argued that there are missed analytical opportunities in this area, given the potential that exploring psychological factors may have on increasing uptake^[62] and the risk that inequalities associated with mental health may intersect with other vulnerabilities^[63].

Some studies have focused on the impact that communication about the risks associated with Covid-19 could have on vaccine acceptance. A cross-cultural representative survey administered in the UK, USA and Turkey reports that risk-based incentives (e.g. knowing people who became very ill or died from Covid-19) were effective in promoting vaccine uptake intention^[64]. Additionally, personal benefit information (e.g. reduced risk of serious disease outcomes or long-term health issues caused by Covid-19) have been found to significantly improve acceptance in those strongly hesitant in a single-blind randomised controlled trial which involved more than 15,000 UK adults between January and February 2021^[65]. This is in line with other research showing the positive effects on uptake deriving from the promotion of vaccines as effective tools in reducing the risk of severe disease from Covid-19^[66].

Other solutions in the literature to address misconceptions and increase awareness of risk include communication campaigns targeting public perceptions through narrative films encouraging identification with the characters^[67], but also the use of public health information highlighting how hesitancy can cause further outbreaks and deaths^[68]. It has also been noted that influencing attitudes on vaccines is potentially more effective at the beginning of a vaccination programme, as perception of risk tends to decrease with the number of vaccinated people increasing (although new variants always have the potential to change this relationship if symptoms begin to be seen as posing a greater risk than side effects)^[69].