Key aspects regarding the introduction and prioritisation of COVID-19 vaccination in the EU/EEA and the UK : Once vaccines against COVID-19 are available, their supply is likely to be limited, at least initially. Supply capacity, both initially and over time, will thus determine vaccine usage and delivery prioritisation. Deployment will need to be adjusted accordingly to promptly optimise vaccine allocation and ensure vaccine availability to those most in need.
The following non-mutually exclusive approaches for vaccine deployment can be considered when building vaccination strategies, taking into account different levels of vaccine supply and stages of the pandemic:
• focusing on selected groups (e.g. individuals at risk of severe COVID-19, essential workers, vulnerable groups);
• vaccinating according to age strata (e.g. all individuals above a certain age);
• targeting groups with an increased risk of exposure and onward transmission of SARS-CoV-2 (e.g. exposurein professional settings, younger adults);
• prioritising geographical regions with high incidence of COVID-19;
• deploying the vaccine to control active outbreaks;
• performing adaptative approaches to be modulated according to circumstances;
• conducting a universal vaccination strategy
Given the anticipated initial shortage, countries will need to identify priority groups for vaccination. A broader characterisation of these groups will need to further categorise them into different priority tiers. The identification of the priority groups, and of the tiers within them, will depend on several factors, including the disease’s epidemiology at the time of vaccine deployment, the evidence of risk of severe disease and of exposure to COVID-19, the preservation of essential societal services and equity principles, among others. In the process of developing an iterative approach for vaccine deployment with varying supply, mathematical modelling may aid public health experts in identifying priority groups for vaccination and in assessing different scenarios and the impact of alternative vaccination strategies. Lessons learned from the 2009 H1N1 influenza pandemic should also be considered.
