SURVIVORS of the Omicron Covid wave have been warned they won’t be able to fend off new Covid strains circulating.
The findings of new research by Imperial College London even apply to those who are triple-jabbed, scientists say.
The study found that those who had previous Omicron illness were not immune to catching it again, including the older BA.1 and BA.2 versions, and newer BA.4 and BA.5 strains.
That’s despite the fact they had an immune boost against previous strains, such as Delta and Alpha.
Professor Danny Altmann, from Imperial’s Department of Immunology and Inflammation, said: “Not only can it break through vaccine defences, it looks to leave very few of the hallmarks we’d expect on the immune system.
“It’s more stealthy than previous variants and flies under the radar, so the immune system is unable to remember it.”
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However, he stressed vaccines are still protective against severe disease and death.
And Omicron has so far caused a milder illness, especially in the fully jabbed.
After someone is infected with Covid, or vaccinated, their body remembers the bug for the next time it is exposed.
The researchers say each individual has their own “immunity imprint” depending on the type of strain they were infected by, and their vaccine doses.
They wanted to understand why so many people catch Omicron a second time around, even when they should have both natural and vaccine protection.
Blood samples from more than 700 UK healthcare workers who received three doses of mRNA vaccine – Pfizer and Moderna – were analysed.
People who had dodged Covid until the Omicron wave showed immunity that crossed over to older strains.
But they showed a reduced boosting against the Omicron variant, according to the findings in the journal Science.
Healthcare workers who had caught Alpha showed a less sustained antibody response against Omicron.
And those infected during the first wave of the pandemic – by the strain first seen in China – and then again later with Omicron lacked any boosting.
Researchers termed this “hybrid immune damping” – when infection from an older Covid strain impairs the immune boosting effect of a later Omicron infection.
Professor Rosemary Boyton, from Imperial’s Department of Infectious Disease and lead author, said: “Getting infected with Omicron does not provide a potent boost to immunity against re-infection with Omicron in the future.
Prof Altmann said: “We have found that Omicron is far from a benign natural booster of vaccine immunity, as we might have thought, but it is an especially stealthy immune evader.
“While our latest findings highlight clear concerns about the nature of Omicron infection, vaccination remains effective against severe disease.
“Those who are eligible to receive a booster should be encouraged to do so.”
Dr Catherine Reynolds, from Imperial’s Department of Infectious Disease, said: “Our study shows that an individual’s vaccination and infection history can have a huge bearing on their immune response to variants, including to Omicron.”
The researchers said understanding the variety in people’s “Immunity imprint” will be vital moving forward as new Covid strains crop up.
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The BA.2 variant – which caused a record wave of infections in spring this year – remains the dominant strain in the UK.
But newer variants BA.4 and BA.5 have been spreading at higher levels in recent weeks, with a jump of infections from the original BA.1.
