Covid-19 vaccines should target only omicron for best immune response
Covid-19 vaccines may offer better protection if they just target the omicron variant, rather than both omicron and the ancestral SARS-CoV-2 strain
By Clare Wilson
22 November 2023
The omicron variant is dominant worldwide, prompting many countries to adapt their vaccine response
Backyard Productions/Alamy
“Bivalent” covid-19 vaccines based on proteins from the initial SARS-CoV-2 coronavirus as well as the more recent omicron variant may be less effective than those that just target omicron, a study suggests.
The findings come not from a randomised trial, the best kind of medical evidence, but from studying people’s responses to natural infections.
Bivalent vaccines are being offered in several countries, including the UK, Australia, New Zealand and Canada. In the US, however, the vaccines on offer are based just on the omicron variant.
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The first vaccines used during the covid-19 pandemic were based on the “spike” protein of the original coronavirus strain that started spreading worldwide in early 2020.
By the end of 2021, however, the first omicron variants arrived, quickly displacing the previous ones. Omicron was so different that a lot of people started getting infected by it despite being vaccinated against the original virus, although the vaccines still worked well at reducing deaths and hospitalisations.
