Abstract The emergence and rapid spread of SARS-CoV-2 variants may impact vaccine efficacy significantly 1 . The Omicron variant termed BA.2, which differs genetically substantially from BA.1, is currently replacing BA.1 in several countries, but its antigenic characteristics have not yet been assessed 2,3 . Here, we used antigenic cartography to quantify and visualize antigenic differences between SARS-CoV-2 variants using hamster sera obtained after primary infection. Whereas early variants are antigenically similar, clustering relatively close to each other in antigenic space, Omicron BA.1 and BA.2 have evolved as two distinct antigenic outliers. Our data show that BA.1 and BA.2 both escape (vaccine-induced) antibody responses as a result of different antigenic characteristics. Close monitoring of the antigenic changes of SARS-CoV-2 using antigenic cartography can be helpful in the selection of future vaccine strains.

Omicron BA.1 and BA.2 are antigenically distinct SARS-CoV-2 variants