Fast-evolving COVID variants complicate vaccine updates

As countries brace for another Omicron wave driven by the variants BA.4 and BA.5, calls to update COVID-19 vaccines are growing louder. Existing vaccines based on the version of the virus SARS-CoV-2 that emerged in Wuhan, China, in late 2019 are a poor match to current Omicron strains. As a result, the vaccines now offer only short-lived protection from infection — although they seem to be holding up against severe disease. This week, an advisory panel to the US Food and Drug Administration (FDA) will meet to discuss whether COVID-19 vaccines should be updated — and what the upgraded vaccines should look like.