Long-term spatial patterns in COVID-19 booster vaccine uptake

TL;DR

The study shows that booster vaccine uptake in Scotland has dropped in high-risk groups, such as the elderly and those in deprived areas, which could worsen the impact of ongoing COVID-19 transmission.

Contribution

The paper introduces a method using public demographic data and Random Forests to predict future booster uptake patterns and highlights the growing influence of deprivation on vaccination trends.

Findings

Age and sex are the strongest predictors of booster vaccine uptake in Scotland.

Community deprivation and ethnic minority proportions significantly influence uptake patterns.

Differences between first and second boosters suggest deprivation's impact on uptake will likely increase over time.

Abstract

Vaccination is a critical tool for controlling infectious diseases, with its use to protect against COVID-19 being a prime example. Where a disease is highly transmissible, even a small proportion of unprotected individuals can have substantial implications for disease burden and control. As factors such as deprivation and ethnicity have been shown to influence uptake rates, identifying how uptake varies with socio-demographic indicators is critical for reducing hesitancy and issues of access and identifying plausible future uptake patterns.

We analyse COVID-19 booster vaccinations in Scotland, subdivided by age, sex, dose and location. Linking to public demographic data, we use Random Forests to fit patterns in first booster uptake, with systematic variation restricted to  ~ 1km in urban areas. We introduce a method to predict future distributions using our first booster model, assuming existing trends over deprivation will persist. This provides a quantitative estimate of the impact of changing motivations and efforts to increase uptake.

While age and sex have the greatest impact on the model fit, there is a substantial influence of community deprivation and the proportion of residents belonging to a black or minority ethnicity. Differences between first and second boosters suggest in the longer-term that the impact of deprivation is likely to increase.

This would further the disproportionate impact of COVID-19 on deprived communities. Our methods are based solely on public demographic data and routinely recorded vaccination data, and would be easily adaptable to other countries and vaccination campaigns where data recording is similar.

A key line of defence against many infectious diseases is vaccination, and it is especially important to vaccinate people at the highest risk of becoming seriously unwell if infected. For COVID-19, this includes (amongst others) the elderly and people living in more deprived areas. Looking at Scottish vaccine data and comparing it to data on how deprived different areas in Scotland are, we show how uptake has dropped off in some of these at-risk groups. This is different from the early stages of the pandemic, when there was more motivation to get vaccinated so life could get back to normal. This is concerning because, although we are no longer in a pandemic, COVID-19 continues to circulate in high numbers, and the protection offered by a COVID-19 vaccine is relatively short-lived. The findings of this study suggest that those at-risk groups should be specifically targeted for booster vaccinations moving forward.

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