Omicron is in fact a “stealthy immune evader”, a study published in the Science journal found.
It can break through vaccine defences and “flies under the radar” so the immune system is unable to remember it, Professor Danny Altmann said from the Department of Immunology and Inflammation.
Omicron provides a “poor natural boost of Covid-19 immunity against re-infection… even in people who are triple vaccinated”, the study found.
The new findings quash a common assumption that people who have caught the variant will better fend off re-infection in the future.
“Those infected during the first wave of the pandemic and then again later with Omicron lacked any boosting,” the paper said.
The findings aim to explain why repeat infections have been common during the spread of the Omicron variant.
“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,” said Professor Altmann.
"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.”