A lack of perceived benefits and a gap in knowledge distinguish the vaccine hesitant from vaccine accepting during the COVID-19 pandemic

Abstract

Somewhere between 60 and 90% of populations need to be immune to the coronavirus disease 2019 (COVID-19) to stop its spread (Anderson, Vegvari, Truscott, & Collyer, 2020). Mass vaccination programmes are underway, yet around 32% of people worldwide may refuse a vaccine (Wang et al., 2020). Ending the pandemic depends on individual decision-making. Hesitancy varies by socio-demographic background, but the variance explained is small (Freeman et al., 2020). This limits the effectiveness of targeting public health communication by social groups. A better method to inform communication may be to investigate what influences the decisions of vaccine-hesitant individuals. This study uses behavioural science to investigate how people decide whether to take a COVID-19 vaccine. Given variation in experiences of and emotional responses to the pandemic, people may vary in perceptions of the benefits and risks of vaccines, with implications for how they resolve the trade-offs. Trade-off decisions are influenced by level of expertise (Shaddy, Fishbach, & Simonson, 2021). Yet little is known about how much people know about COVID-19 vaccines. Most research was carried out before details about approved vaccines were publicly available. We know of no research that investigated how knowledge about the vaccines themselves relates to intention. A large (N = 1600) nationally representative sample in the Republic of Ireland carried out a series of interactive computerised tasks, online between 21 and 27 January 2021. Ireland was experiencing a third wave of infections and strong public health restrictions. The vaccine programme had begun but most people had not yet been offered a vaccine. Participants were first asked whether they definitely would, probably would, probably would not or definitely would not get a COVID-19 vaccine, with an option for those unable to take it. An interactive computerised environment systematically manipulated the factors that participants were asked to consider at one time. Participants listed, in open text boxes, the risks and benefits of the vaccine that came to mind. They also ranked a list of potential risks and benefits, made explicit trade-offs between them to determine relative influence, and completed a knowledge test about COVID-19 vaccines. The test comprised 13 multiple choice questions, making a total score of 0–18 (some had multi-select options). The test covered efficacy, side effects, development, herd immunity, and misinformation. Socio-demographic variables and perceived severity of and susceptibility to COVID-19 were also collected. Research questions, methods and hypotheses were pre-registered on Open Science Framework and reported in a preprint (Robertson, Mohr, Barjaková, & Lunn, 2021). The research was funded by the Irish Government’s Department of Health and approved under the ESRI’s ethical review policy. Intention was close to expectations: 67.1% said they would accept a COVID-19 vaccine, 21.1% leaned towards yes, 6.2% leaned towards no and 4.9% said they would not. There are two key findings: hesitant participants differed from accepting participants more in how they called to mind the benefits of the vaccine than in how they called to mind the risks. Second, hesitant participants had a substantial gap in knowledge compared to accepting participants. In open text responses, vaccine-hesitant participants were less likely to list any benefits of COVID-19 vaccines, even when asked explicitly to write down any risks and benefits they could think of. The effect was large: 91% of the most accepting group reported at least one benefit, but only 5% of the most hesitant (Fig. 1).