Epidemiological characteristics of the B.1.526 SARS-CoV-2 variant

Background: The B.1.526 variant (WHO designation: Iota) is a SARS-CoV-2 variant of interest, as classified by both the US CDC and the WHO. Due to a lack of extensive genomic sequencing and contact tracing data, its key epidemiological properties have not been well characterized. Methods: We utilized nine epidemiological and population datasets collected in New York City (NYC), where B.1.526 emerged, and comprehensive modeling to estimate the changes in transmissibility, immune escape potential, and infection fatality risk (IFR) for B.1.526. Findings: Estimated transmission rate in the neighborhood where B.1.526 was initially detected was consistently higher than other neighborhoods in NYC and further increased during the weeks preceding B.1.526 detection, likely due to its early spread there. Overall, models estimated that B.1.526 had transmissibility about 15-25% higher than previously circulating variants and that it could escape immunity in 0-10% of previously infected persons. In addition, B.1.526 substantially increased IFR in older adults: by 46% (95% CI: 7.4 - 84%) among 45-64 year-olds, 82% (95% CI: 20 - 140%) among 65-74 year-olds, and 62% (95% CI: 45 - 80%) among 75+ during Nov 2020 - Apr 2021, compared to baseline IFR estimated for preexisting variants. Interpretation: New variants like B.1.526 likely spread in the population weeks prior to detection, and partial immune escape (e.g., resistance to therapeutic antibodies) could offset prior medical advances and increase IFR. Early preparedness for and close monitoring of SARS-CoV-2 variants, their epidemiological characteristics, and disease severity are thus crucial to COVID-19 pandemic response as it remains a global public health threat.