Implementing behavioural science informed letter interventions to increase COVID-19 vaccination uptake in uncontactable London residents: a difference-in-difference study in London, UK.

BACKGROUND: The UK COVID-19 vaccination programme began in December, 2020. By February, 2021, eight North West London Clinical Commissioning Groups (CCGs) had the lowest vaccination rates nationally. This study evaluated the impact of behavioural science-informed (BI) letters on vaccination uptake. METHODS: Unvaccinated residents of the Central London CCG who were deemed uncontactable (through text messaging and phone calls) were identified with the whole systems integrated care database. BI letters were sent to residents in the intervention CCG between May and June, 2021. Three neighbouring CCGs in London with similar non-responder data were used as control groups. A linear difference-in-difference analysis was undertaken to assess change in vaccine uptake rate across all four CCGs. Percentage point change was adjusted for selected covariates including ethnicity, age, gender, and index of multiple deprivation (IMD) quintiles. Approval was obtained from the quality improvement and audit office of Imperial College Healthcare NHS Trust (London, UK). FINDINGS: Within the intervention Central London CCG, 10 161 residents received the BI letter. The control CCGs contained 27 383 uncontactable residents. All CCGs showed an increase in vaccination rates in this population. The linear difference-in-difference analysis showed an increase in vaccination uptake in the intervention CCG (relative change 31·9% (95% CI 30·5-33·3; p<0·0001). Residents in IMD quintile 5 (least deprived) showed the largest rate of change (4·1%; p<0·0001). Residents with a mixed or multiple ethnic background were less likely to receive a COVID-19 vaccine (-4·1%, p<0·0001). INTERPRETATION: BI letters improved the rate of vaccine uptake. The percentage point increase of 31·9% equates to 436 additional previously uncontactable residents being vaccinated. Our data highlighted differences in the effect of BI-informed interventions in population subgroups. BI letters are a cost-effective and trusted communication tool, effectively engaging residents where other communication strategies did not work. FUNDING: None.

Testing the impact of differing behavioural science informed text message content in COVID-19 vaccination invitations on vaccine uptake: A randomised clinical trial.

Behavioural science constructs can be incorporated into messaging strategies to enhance the effectiveness of public health campaigns by increasing the occurrence of desired behaviours. This study investigated the impact of behavioural science-informed text message strategies on COVID-19 vaccination rates in 18-39-year-olds in an area of low uptake in London during the first vaccination offer round in the United Kingdom. This three-armed randomised trial recruited unvaccinated residents of an urban Central London suburb being offered their first vaccination between May and June 2021. Participants were randomised to receive the control (current practice) text message or one of two different behavioural science-informed COVID-19 vaccine invitation strategies. Both intervention strategies contained the phrase "your vaccine is ready and waiting for you", aiming to evoke a sense of ownership, with one strategy also including a pre-alert message. The main outcome measures were vaccination rates at 3 and 8 weeks after message delivery. A total of 88,820 residents were randomly assigned to one of the three trial arms. Each arm had a vaccine uptake rate of 27.2 %, 27.4 % and 27.3 % respectively. The mean age of participants was 28.2 years (SD ± 5.7), the mean index of multiple deprivation was 4.3 (SD ± 2.0) and 50.4 % were women. Vaccine uptake varied by demographics, however there was no significant difference between trial arms (p = 0.872). Delivery was successful for 53.6 % of text messages. Our choice of behavioural science informed messaging strategies did not improve vaccination rates above the rate seen for the current practice message. This likely reflects the wide exposure to public health campaigns during the pandemic, as such text messages nudges were unlikely to alter existing informed decision-making processes. Text message delivery was relatively low, indicating a need for accurate mobile phone number records and multi-modal approaches to reach eligible patients for vaccination. The protocol was registered at clinicaltrials.gov (NCT04895683) on 20/05/2021.