Implementing behavioural science-informed letter interventions to increase COVID-19 vaccination uptake in London...

The accelerated development of vaccines to mitigate COVID-19 was crucial in the response to the 2020 pandemic. The success of vaccination strategies relies upon adequate uptake across the population. In the United Kingdom, COVID-19 vaccination began in December 2020, with population groups invited in priority groups according to age and clinical vulnerability. By February 2021, uptake rates were lower in North West London than the national average. This study aimed to explore whether behaviourally-informed (BI) letters could increase the rate of first vaccine uptake in previously uncontactable residents. BI letters were designed to invoke a sense of ownership, and highlight the ease of accessing a vaccine. Letters were sent to unvaccinated uncontactable residents in a Central London Borough over a 3-week period. Three neighbouring boroughs in London with similar non-responder data acted as controls. A linear difference in difference (DID) analysis assessed the change in the rate of vaccine uptake across all four boroughs, with percentage point change adjusted for covariates including ethnicity, age, gender and socioeconomic status. In total, 10,161 residents in Central London were eligible to receive our BI letter. All four boroughs demonstrated an increase in vaccination, with an absolute increase of 4.3 % in the intervention borough. Our linear DID analysis showed a 14.7 % increase in vaccination likelihood in the intervention borough following the intervention on average across all weeks included in the study. Residents with a mixed or multiple ethnic background were less likely to receive a COVID-19 vaccination. Those from a more deprived socioeconomic background demonstrated the largest rate of change. Our study highlights the effectiveness of traditional communication strategies such as letters in those who are uncontactable by other means. Incorporating behavioural science principles into healthcare communication, such as those designed to evoke a sense of ownership can enhance their effectiveness.