In a year that began with the Alpha and Beta variants (then known as B.1.1.7 and B.1.351, or the “UK variant” and “South African variant”) dominating headlines, and ends with skyrocketing Omicron case numbers in multiple countries, researchers have learned much about the mutations the variants are accumulating, as well as the changes they wreak in the virus’s epidemiology. Some variants, such as Alpha and later Delta, became dominant, while others, including Mu, looked worrying but never spread widely. For those tracking SARS-CoV-2’s evolution, Omicron threw a curveball, its dozens of mutations indicating it split off from other known variants around the middle of last year. How it managed to evolve so long without detection—for example, in an immunocompromised person with a long-term infection, or in an animal population that caught the virus from people—remains a matter of speculation.
The picture looked rosy for vaccines at the beginning of the ...
