Background Large-scale vaccination is fundamental to combatting COVID-19. In March 2021, the UK’s vaccination programme had delivered vaccines to large proportions of older and more vulnerable population groups; however, there was concern that uptake would be lower among young people. This research was designed to elicit the preferences of 18–29-year-olds regarding key delivery characteristics and assess the influence of these on intentions to get vaccinated, to inform planning for this cohort. Methods From 25 March to 2 April 2021, an online sample of 2012 UK adults aged 18–29 years participated in a Discrete Choice Experiment. Participants made six choices, each involving two SMS invitations to book a vaccination appointment and an opt-out. Invitations had four attributes (1 × 5 levels, 3 × 3 levels): delivery mode, appointment timing, proximity, and sender. These were systematically varied according to a d-optimal design. Responses were analysed using a mixed logit model. Results The main effects logit model revealed a large alternative-specific constant (β = 1.385, SE = 0.067, p < 0.001), indicating a strong preference for ‘opting in’ to appointment invitations. Pharmacies were dispreferred to the local vaccination centre (β = − 0.256, SE = 0.072, p < 0.001), appointments in locations that were 30–45 min travel time from one’s premises were dispreferred to locations that were less than 15 min away (β = − 0.408, SE = 0.054, p < 0.001), and, compared to invitations from the NHS, SMSs forwarded by ‘a friend’ were dispreferred (β = − 0.615, SE = 0.056, p < 0.001) but invitations from the General Practitioner were preferred (β = 0.105, SE = 0.048, p = 0.028). Conclusions The results indicated that the existing configuration of the UK’s vaccination programme was well-placed to deliver vaccines to 18–29-year-olds; however, some adjustments might enhance acceptance. Local pharmacies were not preferred; long travel times were a disincentive but close proximity (0–15 min from one’s premises) was not necessary; and either the ‘NHS’ or ‘Your GP’ would serve as adequate invitation sources. This research informed COVID-19 policy in the UK, and contributes to a wider body of Discrete Choice Experiment evidence on citizens’ preferences, requirements and predicted behaviours regarding COVID-19.

Misinformation can have a profound detrimental impact on populations’ wellbeing. In this large UK-based online experiment (n = 2430), we assessed the performance of false tag and inoculation interventions in protecting against different forms of misinformation (‘variants’). While previous experiments have used perception- or intention-based outcome measures, we presented participants with real-life misinformation posts in a social media platform simulation and measured their engagement, a more ecologically valid approach. Our pre-registered mixed-effects models indicated that both interventions reduced engagement with misinformation, but inoculation was most effective. However, random differences analysis revealed that the protection conferred by inoculation differed across posts. Moderation analysis indicated that immunity provided by inoculation is robust to variation in individuals’ cognitive reflection. This study provides novel evidence on the general effectiveness of inoculation interventions over false tags, social media platforms’ current approach. Given inoculation’s effect heterogeneity, a concert of interventions will likely be required for future safeguarding efforts.

BackgroundLarge-scale vaccination is fundamental to combatting COVID-19. In March 2021, the UK’s vaccination programme had delivered vaccines to large proportions of older and more vulnerable population groups; however, there was concern that uptake would be lower among young people. This research was designed to elicit the preferences of 18-29-year-olds with respect to key delivery characteristics.MethodsFrom 25 March - 2 April 2021, an online sample of 2,021 UK adults aged 18-29 years participated in a Discrete Choice Experiment. Participants made six choices, each between two SMS invitations to get vaccinated; each choice also had an opt-out. Each invitation had four attributes (1 x 5 levels, 3 x 3 levels): delivery mode, appointment timing, proximity, and SMS sender. These were systematically varied according to a d-optimal fractional factorial design. Order of presentation was randomised for each participant. Responses were analysed using a mixed logit model.ResultsThe logit model revealed a large alternative-specific constant (β = 1.385, SE = 0.067, p <0.001), indicating a strong preference for ‘opting in’ to appointment invitations. Pharmacies were dispreferred to the local vaccination centre (β = -0.256, SE = 0.072, p <0.001), appointments in locations that were 30-45 minutes travel time from one’s premises were dispreferred to locations that were less than 15 minutes away (β = -0.408, SE = 0.054, p <0.001), and, compared to invitations sent by the NHS, SMSs forwarded by ‘a friend’ were dispreferred (β = -0.615, SE = 0.056, p <0.001) but invitations from the General Practitioner were preferred (β = 0.105, SE = 0.048, p = 0.028).ConclusionsThe results indicated that the existing configuration of the UK’s mass vaccination programme was well-placed to deliver vaccines to 18-29-year-olds; however, some adjustments might enhance acceptance. Local pharmacies were not preferred; long travel times were a disincentive but close proximity (0-15 minutes from one’s premises) was not necessary; and either the ‘NHS’ or ‘Your GP’ would serve as adequate invitation sources. This research informed COVID-19 policy in the UK, and contributes to a wider body of Discrete Choice Experiment evidence on citizens’ preferences, requirements and predicted behaviours regarding COVID-19.

Misinformation can have a profound detrimental impact on populations’ wellbeing. In this large UK-based online experiment (n=2,430), we assessed the performance of false tag and inoculation interventions in protecting against different forms of misinformation (‘variants’). While previous experiments have used perception- or intention-based outcome measures, we presented participants with real-life misinformation posts in a social media platform simulation and measured their engagement, a more ecologically valid approach. Our pre-registered mixed-effects models indicated that both interventions reduced engagement with misinformation, but inoculation was most effective. However, random differences analysis revealed that the protection conferred by inoculation differed across posts. Moderation analysis indicated that immunity provided by inoculation is robust to variation in individuals’ cognitive reflection.This study provides novel evidence on the general effectiveness of inoculation interventions over false tags, social media platforms’ current approach. Given inoculation’s effect heterogeneity, a concert of interventions will likely be required for future safeguarding efforts.