A new study by researchers at Imperial College London found no evidence of a difference in severity between the Omicron variant of covid-19 and the Delta variant. The risk of reinfection, however, is 5.4 times higher. Previous infection or a two-dose vaccine regimen offer no more than 20% protection against symptomatic cases of Omicron—but a booster from an mRNA jab can push this figure up to 55-80%. Omicron is quickly supplanting other strains: it now dominates in England, accounting for 54% of cases. Public-health agencies logged record infections on Friday—in Britain, New York state and — The Economist Espresso, Morning Briefing, December 18, 2021