Estimating SARS-CoV-2 variant strain infectiousness in Japan as of March 28, 2021
Abstract
Background
A variant strain of SARS-CoV-2, VOC202012/01, emerged in the UK in September, 2020. Its infectiousness was estimated as higher than that of the original strain.
Object
We estimated the infectiousness of the variant strain of SARS-CoV-2 in comparison to that of the original strain under conditions prevailing in Japan.
Methods
We estimated infectiousness through a simple susceptible–infected–recovered (SIR) model by strain. The study period was March 1–28, 2020. The information used for the study was available as of April 3, 2020.
Results
The estimated reproduction number of the SARS-CoV-2 variant strain was 1.799; its 95% CI was [1.642, 1.938]. The onset date of the first case in Japan was estimated as December 4 ([November 16, December 14]), 2020. However, infectiousness of the original strain was estimated as 1.123 ([1.093, 1.166]).
Discussion and Conclusion
We demonstrated that infectiousness increased by 0.684 or 60%, increasing from the original to the variant. That finding might be comparable to that of a study conducted in the UK. However, the difference must be monitored continuously and carefully.
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