Dec 16: What more we know about Omicron

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Infections of the Omicron variant are spiralling globally. The UK, reeling under separate outbreaks of the variant as well as Delta, set a record for new cases on Wednesday and logged a 10% increase in hospitalisation compared to last week. The worst, England’s chief medical officer Chris Whitty warned, may yet to come as Omicron takes over.

Across the English Channel, France responded by banning people from entering from the UK, while on the other side of the Atlantic, officials in the US confirmed regular vaccine doses may become insufficient and boosters will be crucial.

Globally, there are more than 75 countries that have confirmed cases of Omicron and scientists are racing to uncover how the mutated virus will shape the next few months of the pandemic, which is almost certain to flare in several regions of the world.

Are boosters enough?

On Wednesday, White House medical adviser Anthony Fauci said Omicron has not mutated enough to need redesigned vaccine (or a booster), and third doses of the existing jabs work adequately.

Fauci’s comments are based on a body of scientific evidence unveiled recently. Researchers from the National Institute of Allergy and Infectious Diseases (NIAID) and Johns Hopkins University last week published preliminary findings that suggest the adaptive immune response of the human body – which learns a pathogen and can later identify and kill infected cells – recognises Omicron almost as effectively as it does the other variants.

This is different from the case of another component of the immune system, which consists of antibodies that bind to circulating viral particles before they can infect cells. Antibodies created in response to an infection with one of the older variants or via vaccination are less able to bind to Omicron.

The authors said this is because Omicron has mostly not mutated in regions that the adaptive immunity’s killer T cells target. “These data suggest that virtually all individuals with existing anti-Sars-CoV-2 CD8+ T-cell responses should recognise the Omicron VOC, and that Sars-CoV-2 has not evolved extensive T-cell escape mutations at this point,” the authors said in the study, and added that those with vaccination and a past infection will still have protection from Omicron-triggered Covid-19.

Or should vaccines be updated?

But two other studies contend that the evolution of Omicron represents a striking leap that could necessitate the work on revising vaccines, even if they are for a future, even-worse configuration of the virus that looks increasingly inevitable.

In the first study, the scientists (a group comprising teams from Switzerland, US and Italy) said they found that antibodies trained on one part of the Sars-Cov-2, known as the receptor binding domain of the Spike protein, were largely ineffective in neutralising Omicron.

But antibodies that target other parts of the virus retained ability to neutralise even Omicron, since those parts did not undergo as significant a mutation in the new variant.

Almost all vaccines at present target the spike protein of the virus, which has evolved significantly in Omicron.

The first study also found that Omicron had gained an ability to bind to mouse ACE2, an enzyme the Sars-Cov-2 previously couldn’t attach to.

The second study, by researchers from Hong Kong and the US, too found that most antibodies that target the spike had become ineffective. “The Omicron variant presents a serious threat to many existing Covid-19 vaccines and therapies, compelling the development of new interventions that anticipate the evolutionary trajectory of Sars-CoV-2,” the study said.

The authors of this study called for efforts to be made to pre-empt further evolution of the coronavirus. “It is not too far-fetched to think that this Sars-CoV-2 is now only a mutation or two away from being pan-resistant to current antibodies… We must devise strategies that anticipate the evolutional direction of the virus and develop agents that target better conserved viral elements.”

Fauci, writing separately along with two other American experts in the New England Journal of Medicine, pitched for a universal coronavirus vaccine.

“We need a research approach that can characterise the global ‘coronaviral universe’ in multiple species, characterise the natural history and pathogenesis of coronaviruses in laboratory animals and in humans, and apply this information in developing broadly protective ‘universal’ vaccines (protecting against all betacoronaviruses, and ideally all coronaviruses),” they wrote in the piece published on Wednesday.

Until that happens, the Sars-Cov-2 is “unlikely to be eliminated, let alone eradicated; it will probably continue to circulate indefinitely in periodic outbreaks and endemics”, they said.

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