The potential impact of Omicron and future variants of concern on SARS-CoV-2 transmission dynamics and public health burden: a modelling study

SARS-CoV-2 variant Omicron (B.1.1.529) was classified as a variant of concern (VOC) on November 26, 2021. (1, 2) The infectivity, severity, and immune evasion properties of Omicron relative to the Delta variant would determine 1) the probability of dominant future transmission, and 2) the impact on disease burden. (3, 4) Here we apply individual-based transmission model OpenCOVID to identify thresholds for Omicron’s or any VOC’s potential future dominance, impact on health, and risk to health systems; and identify for which combinations of viral properties, current interventions would be sufficient to control transmission. We show that, with first-generation SARS-CoV-2 vaccines (5) and limited physical distancing in place, the threshold for Omicron’s future dominance was primarily be driven by its degree of infectivity. However, we identified that a VOC’s potential dominance will not necessarily lead to increased public health burden. Expanded vaccination, that includes a third-dose for adults and child vaccination strategies, was projected to have the biggest public health benefit for a highly infective, highly severe VOC with low immune evasion capacity. However, a highly immune evading variant that becomes dominant would likely require alternative measures for control, such as strengthened physical distancing measures, novel treatments, and second-generation vaccines. These findings provide quantitative guidance to decision-makers at a critical time while Omicron’s properties are being assessed and preparedness for new VOC’s is eminent. (6) We emphasize the importance of both genomic and population epidemiological surveillance.