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Omicron: 2 doses of Sinopharm vaccine offers weak protection against new strain, finds study

  • Researchers from the University of Washington and Humabs BioMed investigated how Omicron might escape immunity from past infections or vaccination
  • Research confirms recent studies finding mutations on the receptor-binding domain of the spike protein led to immunity escape against available vaccines

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Results of a new study by the University of Washington and Humabs Biomed showed the antibody levels of people vaccinated with Sinopharm’s vaccine dropped significantly against Omicron compared with the older Covid-19 strain. Photo: AFP
The Omicron variant of the coronavirus evades immunity offered by an inactivated Covid-19 vaccine developed by Sinopharm, a lab study has found.
Researchers from the University of Washington and Swiss antibody therapeutics company Humabs BioMed investigated how the Omicron variant might escape immunity from past infections or vaccination by comparing the performance of plasma from recovered Covid-19 patients and people vaccinated with six major Covid-19 vaccines.

They tested how the plasma worked against a pseudovirus genetically modified to resemble the ancestral and Omicron variants of the virus that causes Covid-19. The results of the study, which were not peer-reviewed, were published on BioRxiv.org.

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Results showed the antibody levels of people vaccinated with Sinopharm’s vaccine dropped significantly against Omicron compared with the ancestral, or older, strain and, of the total 13 participants, only three people could be found to produce detectable antibodies that could block the Omicron strain of the virus from entering cells, a process known as “neutralising”.

David Veesler, associate professor at the department of biochemistry at the University of Washington and one of the correspondence authors of the study, said the in vitro studies evaluated plasma neutralising antibodies “which is a correlate of protection against Sars-CoV-2”, the virus that causes Covid-19.

“However, other factors such as T cells [an immune system cell] can play important roles to protect us against pathogens, especially in the absence of neutralising antibodies,” Veesler said.

“It is accurate to say that we could not detect plasma neutralising activity against Omicron in most Sinopharm vaccines. Evaluating vaccine-efficacy in the human population will require epidemiology studies.”

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