Vaccine-makers should stop including the spike protein of the original SARS-CoV-2 coronavirus in covid-19 booster jabs to make them more effective against current variants, a study of antibody responses has concluded.
The first covid-19 vaccines were based on a SARS-CoV-2 genome sequence from Wuhan, China, on 11 January 2020. From this, researchers determined the sequence of the spike protein on the outside of the virus and started creating vaccines based on it. Moderna had the first doses of its mRNA vaccine ready for testing by 24 February 2020.
But by the time the first vaccines were approved and vaccination campaigns got under way towards the end of 2020, new variants of SARS-CoV-2 were emerging. These had mutations that changed the shape of key parts of the spike protein, meaning antibodies targeting the original spike didn鈥檛 bind to it as well.
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This reduced the vaccines鈥� effectiveness at preventing infections, though they remained highly effective at preventing serious disease. After the omicron variant emerged with even more extensive changes towards the end of 2021, vaccine-makers began to prepare booster vaccines based on the omicron spike protein.
When vaccines such as annual flu jabs are updated, they normally contain only the new variant or variants. But vaccine companies made 鈥渂ivalent鈥� covid-19 booster vaccines containing both the original and omicron spikes, in large part because of regulations making it simpler to get approval for such boosters, says at the University of Michigan.
There has been controversy about whether these bivalent boosters are better than monovalent boosters containing only the original spike. Recent studies suggest that bivalent boosters against severe disease 鈥� but aren鈥檛 much better .
Gordon鈥檚 team has now looked in detail at the antibodies produced by 72 people who, after the first three vaccine doses, got either a monovalent booster, a bivalent booster or an omicron infection. The researchers found that the types of antibodies produced in response to the bivalent booster were similar to those after a monovalent vaccine, and were still focused on the original spike.
By contrast, in those infected by omicron, there was a shift in focus, with more new antibodies specifically targeting the omicron spike protein.
This is an example of 鈥渋mmunological imprinting鈥�, according to the team. When the original spike is present, people鈥檚 immune systems are simply revving up the pre-existing response to that protein, instead of producing new antibodies that target the omicron spike.
鈥淚t鈥檚 a good study,鈥� says at Imperial College London. The original spike is 鈥渆ssentially a vaccine for an extinct virus not seen on the planet since 2021鈥�.
The World Health Organization (WHO) has come to the same conclusion based on related findings. It 鈥渁dvises moving away from the inclusion of the index [original] virus in future formulations of COVID-19 vaccines鈥�, it said in . The WHO is recommending that the next vaccines should be based on the XBB.1 omicron subvariants now dominant around the world.
The US Food and Drug Administration is meeting on 15 June to decide what should be in the next covid-19 boosters for the US.
bioRxiv
