Omicron can evade the immune protection conferred by COVID-19 vaccines and natural infection, according to a peer-reviewed study which also suggests that the new variant of coronavirus is completely resistant to antibody therapies in use today.
The study, published in the journal Nature on Thursday, also highlights the need for new vaccines and treatments that anticipate how the SARS-CoV-2 virus may soon evolve.
The researchers from Columbia University in the US and the University of Hong Kong noted that a striking feature of Omicron is the alarming number of changes in the variant's spike protein that could pose a threat to the effectiveness of current vaccines and therapeutic antibodies.
The study tested the ability of antibodies generated by vaccination to neutralise Omicron in laboratory tests that pitted antibodies against live viruses and against pseudoviruses constructed in the lab to mimic the variant.
The researchers found that the antibodies from people double-vaccinated with Moderna, Pfizer, AstraZeneca, and Johnson & Johnson COVID-19 vaccines were significantly less effective at neutralising Omicron compared to the original virus.
Antibodies from previously infected individuals were even less likely to neutralise Omicron, they said.
People who received a booster shot of either Pfizer or Moderna vaccines are likely to be better protected, although even their antibodies exhibited diminished neutralising activity against Omicron, the study shows.
"The new results suggest that previously infected individuals and fully vaccinated individuals are at risk for infection with the Omicron variant," said David Ho, a professor at Columbia University Vagelos College of Physicians and Surgeons.
"Even a third booster shot may not adequately protect against Omicron infection, but of course it is advisable to get one, as you will still benefit from some immunity," Ho added.
The researchers noted that the findings 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 Omicron.
The study also suggests that all of the monoclonal antibody therapies currently in use and most in development are much less effective against Omicron.
Monoclonal antibodies are laboratory-made proteins that mimic the immune system's ability to fight off harmful pathogens such as viruses.
In neutralisation studies with monoclonal antibodies, only one -- Brii198 approved in China -- maintained notable activity against Omicron, according to the researchers.
A minor form of Omicron is completely resistant to all antibodies in clinical use today, they said.
The study authors note that Omicron is now the most complete "escapee" from neutralisation that scientists have seen.
They also identified four new mutations in the spike protein of Omicron that help the virus evade antibodies, a finding that could inform the design of new approaches to combat the variant.
The SARS-CoV-2 virus uses the spike protein to enter and infect the human cells.
The researchers suggest that new vaccines and treatments need to be developed that can better anticipate how the virus is evolving.
"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 added.