Cost-effectiveness of routine COVID-19 adult vaccination programmes in England.

In England, and many other countries, immunity to SARS-CoV-2 infection and COVID-19 disease is highly heterogeneous. Immunity has been acquired through natural infection, primary and booster vaccination, while protection has been lost through waning immunity and viral mutation. During the height of the pandemic in England, the main aim was to rapidly protect the population and large supplies of vaccine were pre-purchased, eliminating the need for cost-effective calculations. As we move to an era where for the majority of the population SARS-CoV-2 infections cause relatively mild disease, and vaccine stocks need to be re-purchased, it is important we consider the cost-effectiveness and economic value of COVID-19 vaccination programmes. Here using data from 2023 and 2024 in England on COVID-19 hospital admissions, ICU admissions and deaths, coupled with bespoke health economic costs, we consider the willingness to pay threshold for COVID-19 vaccines in different age and risk groups. Willingness to pay thresholds vary from less than £1 for younger age-groups without any risk factors, to over £100 for older age-groups with comorbidities that place them at risk. This extreme non-linear dependence on age, means that despite the different method of estimating vaccine effectiveness, there is considerable qualitative agreement on the willingness to pay threshold, and therefore which ages it is cost-effective to vaccinate. The historic offer of COVID-19 vaccination to those 65 and over for the autumn 2023 programme and those over 75 for the spring 2023 programme, aligns with our cost- effective threshold for pre-purchased vaccine when the only cost was administration. However, for future programmes, when vaccine costs are included, the age-thresholds slowly increase thereby demonstrating the continued importance of protecting the eldest and most vulnerable in the population.