According to a study, the novel coronavirus variant Omicron is highly resistant to antibodies from persons who have recovered from the virus as well as those who have received two doses of the Pfizer vaccine.
Research comes amid rising cases of the variant of concern, as designated by the World Health Organisation (WHO).
Multiple antibodies previously used to treat Covid-19 have been found to be ineffective against Omicron, according to the study published in the journal Cell.
The Omicron coronavirus variant has caused widespread concern due to its great potential for transmission and the possibility of thirty-seven different mutations.
The variant was first detected in South Africa and have hit more than hundred countries worldwide.
The Omicron variant of SARS-CoV-2 appears to be spreading faster than any previous variant and may soon dominate globally, the researchers said.
In the study, they used non-hazardous virus-like particles that carry the Omicron spike protein and are well suited for analysis of virus entry and its inhibition.
The spike protein is used by the SARS-CoV-2 virus to enter and infect cells.
Currently, combinations of the antibodies Casirivimab and Imdevimab, and Etesevimab and Bamlanivimab are used to treat COVID-19.
However, the researchers showed that these antibodies are largely ineffective against the Omicron spike. Only one antibody, Sotrovimab, inhibited the Omicron spike, they said.
“Our cell culture studies suggest that most antibodies currently available for COVID-19 therapy will be ineffective against Omicron,” said study first author Markus Hoffmann from German Primate Center.
“Sotrovimab is an exception and could become an important treatment option for Omicron-infected patients,” Hoffmann said.
The researchers further investigated whether patients infected in Germany during the first wave of the pandemic had produced antibodies that protect against the Omicron variant.
While the antibodies inhibited the spike of the virus responsible for the first wave, the researchers had little effect against the Omicron spike.
They assume that these individuals do not have robust immune protection against the Omicron variant, although an inhibition by T cells, which are also produced during infection, remains to be analysed.
Antibodies produced after two immunisations with the Pfizer vaccine also inhibited the Omicron spike significantly less efficiently than the spike proteins of other variants, the researchers said.
A better protective effect was observed after three doses with Pfizer and after heterologous immunisation with AstraZeneca and Pfizer preventives, they said.
These results indicate that dual immunisation with Pfizer may protect less efficiently against the Omicron variant as compared to the Delta variant, according to the study.
Triple immunisation with Pfizer (booster) and cross-vaccination with AstraZeneca/Pfizer could establish stronger protection, it found.
“Our results indicate that antibody therapies for Covid-19 need to be adapted to the Omicron variant. Adaptation of the BioNTech-Pfizer vaccine should also be considered,” said Hoffmann.
“In contrast, triple immunisation with BioNTech-Pfizer (booster) and cross-vaccination with Oxford-AstraZeneca,” Hoffmann added.
