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The highly transmissible Omicron variant of Covid-19 has the potential to evade the immune protection conferred by vaccines and natural infection, as well as render most monoclonal antibody therapy ineffective, according to a new study. The study led by researchers from Columbia University in the US, in collaboration with scientists at the University of Hong Kong, suggests the need for new vaccines and treatments that anticipate how the virus may soon evolve.
A striking feature of the omicron variant is the alarming number of changes in the virus's spike protein that could pose a threat to the effectiveness of current vaccines and therapeutic antibodies.
The new study, published in the journal Nature, tested the ability of antibodies generated by vaccination to neutralise the Omicron variant in laboratory assays that pitted antibodies against live viruses and against pseudoviruses constructed in the lab to mimic Omicron.
The findings showed that antibodies from people double-vaccinated with any of the four most widely used vaccines - Moderna, Pfizer, AstraZeneca, Johnson and Johnson - were significantly less effective at neutralising the Omicron variant compared to the ancestral virus.
Antibodies from previously infected individuals were even less likely to neutralise Omicron.
Individuals who received a booster shot of either of the two mRNA vaccines were found to be better protected, although even their antibodies exhibited diminished neutralising activity against Omicron.
"The new results suggest that previously infected individuals and fully vaccinated individuals are at risk for infection with the omicron variant," said David Ho, Director at Columbia's Aaron Diamond AIDS Research Centre.
"Even a third booster shot may not adequately protect against omicron infection, but of course it is advisable to get one, as you'll still benefit from some immunity," he added.
The results are consistent with other neutralisation studies, as well as early epidemiological data from South Africa and the UK, which show efficacy of two doses of the vaccines against symptomatic disease is significantly reduced against the omicron variant.
Further, the study suggests that all of the monoclonal antibody therapies currently in use and most in development are much less effective against Omicron, if they work at all.
When administered early in the course of infection, monoclonal antibodies has shown to prevent many individuals from developing severe Covid.
In neutralisation studies with monoclonal antibodies, only one (Brii198 approved in China) maintained notable activity against Omicron. A minor form of Omicron is completely resistant to all antibodies in clinical use today, the researchers said.
The researchers note that Omicron is now the most complete "escapee" from neutralisation that scientists have seen.
In this study Ho's lab also identified four new spike mutations in omicron that help the virus evade antibodies, suggestingA the need for new approaches to combat the variant.
"It is not too far-fetched to think that SARS-CoV-2 is now only a mutation or two away from being completely resistant to current antibodies, either the monoclonal antibodies used as therapies or the antibodies generated by vaccination or infection with previous variants," Ho said.
