How Will Emerging SARS-CoV-2 Variants Impact Herd Immunity?

Abstract

A considerable number of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants are now circulating all around the world, some of which can be considered “of concern” because their infectivity and/or pathogenicity and/or capacity to escape immune system recognition are significantly higher than the original “wild-type” strain, thus consequently boosting virus spread within the population, enhancing the risk of developing more severe illness, and/or even causing epidemic rebounds. These emerging variants especially include B.1.1.7, originally identified in the UK and characterized by 56% increased transmission potential, along with B.1.351, initially detected in South Africa and displaying 50% enhanced transmissibility and decreased recognition by host immune system, and P.1, emerged in Brazil and displaying characteristics similar to the B.1.351 strain. We aim to discuss here the impact of these emerging SARS-CoV-2 variants on herd immunity, whereby higher herd immunity threshold would be needed for arresting their circulation, whilst this in turn could be more difficult to achieve due to their stronger “resistance” to the current generation of vaccines.