Global COVID-19 Vaccination Modelling

The COVID-19 pandemic continues to generate high levels of severe disease worldwide. Many countries have still only been able to deliver very minimal vaccination, leaving large bodies of developing infection. Furthermore, even in those that have delivered effective vaccination campaigns, waning immunity coupled with a rapidly evolving virus means disease remains highly prevalent.

In order to facilitate effective vaccination strategies in Low and Middle-Income Countries, the WHO’s SAGE Working Group on COVID-19 Vaccines released a request for focused modelling work to address uncertainties surrounding epidemiological, Social and Economic Impact scenarios of COVID-19 vaccination strategies. This project was developed in response to this call, with the aim to address the following 5 objectives:

  1. Shifting vaccination priorities with high infection-derived immunity.
    • If the focus is to prevent severe disease and death, which use groups should be prioritised for vaccination in high seroprevalence settings (and which use groups would derive relatively little benefit from vaccination)?
    • What serological data are needed to formulate a serology-informed national policy on vaccination?
  2. Cost-effectiveness of COVID-19 vaccines (compared to other vaccines).
    • For yet (largely) unvaccinated LMICs, in which use groups would vaccination be cost effective?
    • For well vaccinated countries, in which use groups would a fourth/fifth dose in Autumn 2022 (or annually) be cost-effective?
  3. Impact of Variants of Concern (VoC) on vaccination priorities.
    • What profile would a VoC have to warrant (re-)vaccination with current vaccines as an “insurance policy”, and which use groups should be prioritised for this?
    • What profile would a VoC have to have to warrant reactive (re-)vaccination with current vaccines in response to a surge in cases?
    • What profile would a VoC have to have to warrant (re-)vaccination with vaccines including new variants or a broadly protective vaccine?
  4. What would be the increased public health impact of a variant-adapted booster compared to boosting with current vaccines?
    • How does the public health impact achieved through variant-adapted vaccines versus current vaccines vary in populations with different levels of infection- versus vaccine induced seroprevalence?
    • What would be the optimal vaccination strategies (for reducing severe disease and for reducing infection rates), e.g. targeting high priority-use groups vs universal boosting, to achieve maximum public health impact?
  5. Under what assumptions about vaccine and variant characteristics would it be cost effective to switch to variant adapted vaccines for boosting?
    • How does the effectiveness of a variant adapted vaccine compare to using original vaccines, and how does this depend on vaccine and variant characteristics?