SARS-CoV-2 Omicron Outbreak in a Dormitory in Saint-Petersburg, Russia

Abstract The B.1.1.529 Omicron variant of SARS-CoV-2 is rapidly spreading, displacing the globally prevalent Delta variant. Before December 16, 2021, community transmission had already been observed in tens of countries globally. However, in Russia, all reported cases had been sporadic and associated with travel. Here, we report an Omicron outbreak at a students’ dormitory in Saint Petersburg, Russia. Out of the 462 sampled residents of the dormitory, 206 (44.6%) tested PCR positive, and 159 (77.1%) of these infections carried the S:ins214EPE insertion, indicating that they were of the Omicron strain. 104 (65%) of Omicron-positive patients have been vaccinated and/or reported previous covid-19. Whole genome sequencing confirmed that the outbreak is caused by the Omicron variant. Phylogenetic analysis showed that the outbreak has a single origin, and belongs to the S:346K sublineage of Omicron which may be characterized by an increased rate of spread, compared to other Omicron sublineages. The rapid spread of Omicron in a population with preexisting immunity to previous variants underlines its propensity for immune evasion.