Alliance for Pandemic Preparedness

June 4, 2021

Interim Estimates of Increased Transmissibility Growth Rate and Reproduction Number of the Covid-19 B.1.617.2 Variant of Concern in the United Kingdom

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  • [Pre-print, not peer-reviewed] A modeling study found that the effective reproduction number of B.1.617.2 (WHO label Delta, first described in India) is almost certainly higher than that of B.1.1.7 (WHO label Alpha). The study used genomically sequenced cases from the UK diagnosed between March and May 2021 and excluded recent travelers in order to reflect local transmission patterns. The study found that the degree of increased transmissibility of B.1.617.2 was large and varied with the distribution of the time from infection to transmission from 43% higher to 115% higher transmissibility compared to B.1.1.7. Given these results, the author suggests that increasing vaccination coverage may not be sufficient to reduce the reproductive number while NPIs are further relaxed. 

Dagpunar. (June 3, 2021). Interim Estimates of Increased Transmissibility Growth Rate and Reproduction Number of the Covid-19 B.1.617.2 Variant of Concern in the United Kingdom. Pre-print downloaded Jun 4 from https://doi.org/10.1101/2021.06.03.21258293