Abstract

As the world recovers from the acute phase of the Covid-19 pandemic, a key issue is how to avert future large waves of hospitalisations and deaths driven by novel SARS -CoV-2 variants. Vaccination booster campaigns play an important role in maintaining the level of immunity in the population and reducing the risk of severe outcomes in infected individuals. In this talk, we present research commissioned by the WHO SAGE Covid-19 Working Group. We consider a wave of infections caused by a novel SARS -CoV-2 variant, and investigate the effects of deploying booster vaccines according to six different age-based prioritisation strategies. We use eight different exemplar countries from around the world as test cases, chosen to cover a range of socioeconomic backgrounds. The aim is to identify which vaccine targeting strategies are most beneficial in terms of reducing infection and severe outcomes of infection, given a limited number of available booster vaccines. This work extends earlier research conducted when the level of both infection- and vaccination-derived immunity was lower than it is now. In all countries considered, we show that prioritising the eldest and most vulnerable individuals for booster vaccination first is expected to lead to the best public health outcomes (e.g. fewest deaths). Assuming sufficient vaccine supply, serology-informed booster vaccination strategies are predicted to be of limited benefit compared to simply vaccinating the most vulnerable individuals in the population. We hope that this research is useful for guiding booster vaccination strategies in countries worldwide.