The role of altruism vs self-interest in COVID-19 vaccination uptake in the United Kingdom

Objectives The aim of the present study was to explore self-interest, kin altruism and non-kin altruism reasons that influence people to vaccinate against COVID-19. Study design This was a cross-sectional study using a fully repeated measures design. Methods Participants (N = 178) answered questions on perceived threat and likelihood of infection, vaccination status and opinion on mandatory vaccination. Participants also rated a set of statements that asked how likely these would influence them and others to vaccinate against COVID-19. Statements reflected self-interest, kin altruism or non-kin altruism. Results Just more than half of the sample (50.8%) reported the likelihood of infection as somewhat or extremely likely, and almost three-fourths (74.2%) reported that COVID-19 posed a minor or moderate threat to their physical health. Almost three-fourths (74.3%) of the sample were vaccinated, with just more than half (56.2%) in favour of mandatory vaccination. A 2 (self/other) × 3 (self-interest/kin altruism/non-kin altruism) fully repeated measures analysis of variance showed that kin-altruistic reasons were rated most highly, regardless of whether this was regarding oneself or others. Participants rated others as having greater self-interest reasons for vaccination compared with oneself, whereas non-kin altruism reasons for vaccination were rated higher for oneself, compared with others. Conclusion Highlighting the benefits of vaccination for close relatives and vulnerable others in the population would be a useful strategy for government to use when urging the public to vaccinate against COVID-19.


Introduction
The impact of the COVID-19 pandemic has been felt worldwide. Global attempts to control the spread of the virus have included imposing restrictions on behaviour with the hope of returning to normality in the United Kingdom by focusing on vaccinating the population.
Vaccination protects not only the individual but also others, either directly (by reducing transmission) or indirectly (via herd immunity). 1 Nonetheless, vaccine uptake depends on a variety of factors and has been shown to be highly variable across different vaccines. 2 It has been estimated that to achieve herd immunity, approximately 80% of the population would need to receive the COVID-19 vaccination to reduce the spread of the disease and to offer protection to those unimmunised, 3 although this figure may vary with the emergence of new variants of the virus. Therefore, it is imperative that empirical research is conducted to examine ongoing factors that contribute to vaccine uptake.
Research suggests that prompting altruism may be a useful strategy to encourage vaccination against COVID-19. 4,5 Ultimately, receiving a vaccine can be seen as an altruistic act because the benefit would be greater to wider society than to the individual. 6 Unvaccinated individuals would receive greater protection as the number of vaccinated individuals increase. However, the cost of infection would be higher for an unvaccinated individual when fewer people have been vaccinated overall. 7 This study aimed to investigate motivations for vaccine uptake in the United Kingdom and whether factors such as altruism contribute to this. Furthermore, altruism can vary depending on the recipient. From an evolutionary perspective, high levels of altruism are more prominent towards kin (those who share genetic material with us) compared with non-kin. 8 The theoretical reasoning lies in evolutionary theory, suggesting altruism increases inclusive fitness (genetic fitness and survival of those who share genetic code with us). We examined whether there were differences between kin altruism, non-kin altruism (altruism towards non-genetic relatives) or self-interest reasons for having the COVID-19 vaccine. We also examined which reasons were perceived to be important for oneself and which reasons were perceived to be important for others.

Participants
One hundred seventy-eight participants took part (42 male, 134 female, and 2 non-binary). The mean age was 33.31 (standard deviation ¼ 12.28; see supplementary materials for demographic information). Participants were recruited from the general population via social media platforms (such as Facebook and Twitter) and undergraduate students via the host universities' research participation scheme. Data were collected between April 2021 and November 2021. This study did not form part of a larger research project.

Materials and procedure
Once informed consent was provided, participants completed the following measures online:

Demographic information
Participants provided their age, gender, education, nationality, and ethnicity.

Perceived threat of infection and vaccine uptake
Two questions were used to assess the participants' perceived likelihood of infection in terms of personal susceptibility ("how likely do you believe it is that you will get infected with Covid-19?") and threat to physical health ("If you got infected with Covid-19, how threatening would it be to your physical health?"). These were rated on a 5-point scale (1¼ not at all to 5¼ extremely).
Two questions were asked about vaccine uptake for participants that may have already received the vaccine ("Have you been vaccinated for Covid-19?" Yes/No) or intentions to receive the vaccine ("If you have not yet received the vaccine, how likely is it that you would get vaccinated for Covid-19 in the future?" 1¼Highly unlikely e 5¼Highly likely).
Finally, one question examined opinions on mandatory vaccination adapted from Reiger, 5 "What do you think of a mandatory Covid-19 vaccination?" (1¼ strongly oppose to 4¼ strongly favour).

Reasons for vaccination
Participant's reasons that influence their decision to vaccinate for COVID-19 was measured using two sets of statements adapted from Robertson et al. 9 First, participants were asked, "How likely is it that the following reasons would influence you to vaccinate against Covid-19?" The statements reflected kin altruism, non-kin altruism or self-interest. For example, participants rated selfinterest statements such as "To prevent me catching coronavirus or getting very ill from it," non-kin altruistic statements such as "To protect others that are clinically vulnerable" and kin-altruistic statements such as "Because a member of my family is vulnerable." Second, participants were asked, "How likely do you think it is that the following reasons would influence others to vaccinate against Covid-19?" The statements were amended to reflect this perspective (e.g. "To prevent them from catching coronavirus or getting very ill from it"). These were rated on a 5-point scale (1¼ extremely unlikely to 5¼ extremely likely).

This research examined participants' perceptions of COVID-19
and reasons for vaccination for both oneself and perceptions of why others would get vaccinated. When asked about perceived likelihood of infection and threat to physical health, 50.8% of participants reported that likelihood of infection was 'somewhat/ extremely likely' with most participants (74.2%) reporting that COVID-19 posed a minor or moderate threat to their physical health. In the current sample, 74.3% were vaccinated (N ¼ 133), and 25.7% (N ¼ 46) were not yet vaccinated. Of the participants not yet vaccinated, 38.9% (N¼ 21) said it was 'highly likely' that they would get vaccinated compared with 25.9% (N¼ 14) who said it was 'highly unlikely' that they would get vaccinated in the future. When asked about mandatory vaccine, 56.2% (N ¼ 100) somewhat/ strongly favoured mandatory vaccines, whereas 43.8% (N ¼ 78) somewhat/strongly opposed mandatory vaccine.
A two-way repeated measures analysis of variance was used to analyse reasons for vaccination for both self and others. The first factor was perspective with two levels (self/others). The second factor was vaccination motives with three levels (self-interest/kinaltruism/non-kin altruism). The dependent variable was the ratings across the reasons for vaccination that influenced participants' motives to get vaccinated.
There was no significant main effect of perspective Simple contrasts reveal significant differences between self-interest and kin altruism reasons (p < 001) and between selfinterest and non-kin altruism reasons (p < .001). As can be seen from Fig. 1, kin-altruistic reasons were rated most highly, regardless of whether this was for self or others; however, participants rated others as having greater self-interest reasons for vaccination compared with themselves, whereas non-kin altruism reasons were rated higher for self, compared with others. Follow-up tests confirmed these difference were significant for self-interest reasons (t (170) ¼ À5.56, p < .001, d ¼ À.42) and for non-kin altruistic reasons (t (170) ¼ 2.8, p ¼ .006, d¼ .21).

Discussion
These findings offer a novel contribution to the literature by highlighting the reasons why people choose to vaccinate against COVID-19. First, kin-altruistic reasons were rated most highly, regardless of whether this was regarding oneself or others. This is consistent with previous research demonstrating that high levels of altruism are more prominent towards kin and fit within an evolutionary framework. 8 Second, we found that participants rated others as having greater self-interest reasons for vaccination compared with themselves, whereas non-kin altruism reasons were rated higher for oneself, compared with others. This suggests that people see others as having the vaccine for selfinterest (possibly selfish) reasons but see themselves having the vaccine for the benefit of others. This aligns with previous research demonstrating that altruistic acts and feeling good about oneself may motivate people to vaccinate. 10 Furthermore, our findings are consistent with Cucciniello et al. 4 and Reiger 5 who found that individuals are responsive to altruistic notions.
Given that one-fourth of our sample were not yet vaccinated, and 25% of these said they were unlikely to vaccinate in the future; findings such as these are vital to inform strategies for public health messaging that may encourage more people to vaccinate against disease. Emphasising the benefits of vaccination for those close to us and how this could potentially help vulnerable others would be a beneficial strategy for government to adopt 4 as opposed, or in addition to, emphasising the positive effects of vaccination to the self.
There are some limitations of this research. First, we did not use established psychometric scales when constructing our variables. Second, there was not an equal number of vaccinated and unvaccinated participants in each group, meaning we were unable to run additional parametric analyses. Third, although our results align with existing data on the role of altruistic motives in vaccination uptake, more research is needed to establish the role of altruism in COVID-19 vaccine uptake, with the use of various methodologies and statistical analyses. Future research aimed at identifying strategies for public health messaging are important, particularly with the continued need for booster vaccinations against COVID-19.

Ethical approval
Ethical approval was granted by the Faculty of Education, Health and Wellbeing's ethics committee at the University of Wolverhampton.

Funding
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.