Omicron and immunity The case for updating covid-19 vaccines for the Omicron variant

V ARIANTS VARY, but how much? Since SARS-CoV-2 was first sequenced at the beginning of 2020 dozens of versions have been identified. Five have been designated “variants of concern” by the World Health Organisation (WHO). The latest is Omicron, which was given its name in November last year and looks set to become the dominant form of the virus almost everywhere.

One question occupying both scientists and politicians is whether covid vaccines would work even better if they were updated to deal with novel variants. Up to and including Delta, first identified in India, and designated a variant of concern in May 2021, the answer has been “no”. But new research, which has mapped differences between all of the important versions of SARS-CoV-2, suggests that, although administering existing vaccines is still useful, Omicron is so different from the others that the answer might now be “yes”.

Researchers in the Netherlands, co-ordinated by Rogier Sanders and Colin Russell of the University of Amsterdam and Dirk Eggink of the Dutch Public Health Institute, acquired blood samples collected from 51 unvaccinated people shortly after they had been infected with various versions of SARS-CoV-2. These included the original, ancestral, strain and the Alpha, Beta, Gamma and Delta variants. (Omicron samples were not available.) They then assessed the antibody response (“neutralising capacity”) of those samples against different antigens—in other words, different versions of the virus, again using the ancestral strain, Alpha, Beta, Gamma and Delta and, this time, Omicron.

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