The effectiveness of mRNA vaccines and antibody therapy is reduced against all three subvariants of Omicron, according to new research.

The study by scientists at Columbia University and the University of Hong Kong showed that only one currently authorised antibody treatment retains its activity against all Omicron subvariants. Omicron is a highly transmissible variant of SARS-CoV-2 that has caused the biggest surge in COVID cases so far in many countries.

Researchers have identified three subvariants of Omicron that share 21 mutations in the spike protein and named them BA.1, BA.1.1 and BA.2. The findings, published in the journal Nature, showed that in neutralisation experiments, all three variants exhibited strong resistance to most of the monoclonal antibodies tested.

Of 19 antibodies, 17 were ineffective against the BA.2 subvariant. The researchers found that bebtelovimab, the latest monoclonal antibody to receive FDA Emergency Use Authorisation, is the only currently available antibody therapy that can adequately treat all three Omicron subvariants. "The emergence of new variants is narrowing our treatment options and challenging the effectiveness of our current vaccines," said David D. Ho, Professor of Medicine at Columbia University Vagelos College of Physicians and Surgeons.

"It is critical that we don't relax prematurely and continue to devise novel strategies to contain this ever-evolving pathogen," he added. In laboratory experiments, the team studied the ability of 19 monoclonal antibodies and the sera from individuals immunised with one of two available mRNA vaccines to neutralise the three known subvariants of Omicron.

The researchers observed a loss of neutralisation activity against BA.1.1 and BA.2 in blood samples from individuals who had received two mRNA shots. However, the decline in neutralisation was less prominent in blood samples from individuals who had received three mRNA shots, reinforcing the importance of booster shots for sustaining immunity.

When Omicron was first identified in November 2021, the dominant variant was BA.1. Since December, BA.1 cases have declined, while BA1.1 cases have risen and now makeup around 40 per cent of all Omicron cases sequenced globally. The BA.2 subvariant currently represents only 10 per cent of all Omicron cases globally but is increasing in prevalence.