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

Terminology

This review will make reference to the term "vaccine hesitancy" as defined by the World Health Organisation Strategic Advisory Group of Experts (WHO SAGE), namely the "delay in acceptance or refusal of vaccination despite the availability of vaccination services"^[13]. This definition accounts for the complex nature of vaccine hesitancy, which varies by context and is influenced by complacency, convenience and confidence.

Complacency refers to the belief that vaccination is not a necessary preventative action due to perceived low risk of a vaccine-preventable disease. Convenience relates to vaccination services and how they are delivered (physical availability, affordability, accessibility or ability to understand). Confidence pertains to trust in vaccine effectiveness and safety, and in the political and healthcare systems that deliver it. The three terms form what has been named the SAGE "3Cs model"^[14].

Based on this model, the term "vaccine hesitancy" covers a broad spectrum of attitudes ranging from acceptance to opposition to all vaccines, with hesitancy sitting in between. In this continuum, people are not always statically confined to one position but may change perspectives and beliefs over time.

Some scholars have criticised the term hesitancy, seen as placing too much emphasis on people's agency (hence implying a degree of blame), while ignoring structural factors such as systemic racism affecting uptake in certain groupings^[15]. Others have suggested that problematising the distinction between those who are hesitant and those strongly resisting any vaccination (anti-vaxxers) could further erode mistrust, hence feeding into rather than targeting the factors determining hesitancy^[16]. Although taking these views into account, the SAGE definition of "vaccine hesitancy" presented above has been adopted in this review for comparability reasons (as the majority of the literature aligns with that).

Furthermore, the terms 'efficacy' and 'effectiveness' will appear in the sections below as they have been used in the studies mentioning them. Conventionally, efficacy refers to the extent to which a vaccine lowers the risk of getting sick when it is measured in a controlled clinical trial. Effectiveness, instead, refers to how the vaccine performs in the real world^[17].

Similarly, there are references in this review to third and booster doses based on the classifications adopted in the sources. Technically, a third dose of a Covid-19 vaccine is offered to those with a severely weakened immune system who may not have generated a full response to the first two doses. A booster dose is instead an additional dose to extend the duration of protection from previous doses^[18]. This distinction does not appear in the PHS dashboard and in sources published since April 2022, where doses are reported numerically for the sake of simplicity (dose 1, 2, 3 and 4).

Finally, this review will not make use of the term 'BAME' (although this is often found in the papers reviewed) and adopts instead 'minority ethnic groups' or 'ethnic minorities' in line with accepted Scottish Government phrasing^[19]. BAME is an acronym for Black Asian Minority Ethnic and carries the risk of misinterpretation of data due to its vagueness which does not allow disaggregation of data for specific groups. It has also been criticised by minority ethnic groups themselves, who found it constructs a fictitious homogenous group^[20].