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Omicron variant resistant to antibodies, two vaccine doses: Study

The research, published in the journal Cell, also shows that several antibodies used to treat COVID-19 will be ineffective against Omicron.

December 31, 2021 / 01:58 PM IST
Representative image: Reuters

Representative image: Reuters

The Omicron variant of coronavirus is largely resistant to antibodies from people who recover from COVID-19 infection, and those vaccinated with two doses of the Pfizer vaccine, according to a study.

The research, published in the journal Cell, also shows that several antibodies used to treat COVID-19 will be ineffective against Omicron.

However, a third dose of the Pfizer vaccine, and mixing Pfizer and AstraZeneca preventives may protect well against the variant.

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.

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COVID-19 Vaccine

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How does a vaccine work?

A vaccine works by mimicking a natural infection. A vaccine not only induces immune response to protect people from any future COVID-19 infection, but also helps quickly build herd immunity to put an end to the pandemic. Herd immunity occurs when a sufficient percentage of a population becomes immune to a disease, making the spread of disease from person to person unlikely. The good news is that SARS-CoV-2 virus has been fairly stable, which increases the viability of a vaccine.

How many types of vaccines are there?

There are broadly four types of vaccine — one, a vaccine based on the whole virus (this could be either inactivated, or an attenuated [weakened] virus vaccine); two, a non-replicating viral vector vaccine that uses a benign virus as vector that carries the antigen of SARS-CoV; three, nucleic-acid vaccines that have genetic material like DNA and RNA of antigens like spike protein given to a person, helping human cells decode genetic material and produce the vaccine; and four, protein subunit vaccine wherein the recombinant proteins of SARS-COV-2 along with an adjuvant (booster) is given as a vaccine.

What does it take to develop a vaccine of this kind?

Vaccine development is a long, complex process. Unlike drugs that are given to people with a diseased, vaccines are given to healthy people and also vulnerable sections such as children, pregnant women and the elderly. So rigorous tests are compulsory. History says that the fastest time it took to develop a vaccine is five years, but it usually takes double or sometimes triple that time.

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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.
PTI
first published: Dec 31, 2021 01:58 pm
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