‘Centaurus’: virologists express concern at new Covid subvariant

Virologists have voiced concerns about the emergence of another fast-spreading Omicron variant, which is rapidly gaining ground in India and has already arrived in the UK.

The warning came as MPs called for redoubled efforts to persuade the nearly 3 million adults in England who have not yet received a single dose of Covid vaccine, to take up the offer of vaccination.

The BA.2.75 variant – nicknamed “Centaurus” – was first detected in India in early May. Cases in the UK have since risen steeply – and apparently faster than those of the extremely transmissible BA.5 variant, which is also present in India, and is rapidly displacing the previously dominant BA.2 variant in many countries.

BA.2.75 has also since been detected in about 10 other countries, including the UK, US, Australia, Germany and Canada.

The European Centre for Disease Prevention and Control (ECDC) designated it a “variant under monitoring” on 7 July, meaning there is some indication that it could be more transmissible or associated with more severe disease, but the evidence is weak or has not yet been assessed.

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The World Health Organization (WHO) is also closely monitoring the new variant, although its chief scientist, Dr Soumya Swaminathan, said there were not yet enough samples to assess its severity.

In addition to its apparent rapid growth and wide geographical spread, virologists have been alerted by the sheer number of extra mutations BA.2.75 contains, relative to BA.2, from which it is likely to have evolved. “This could mean that it has had the chance to evolve an advantage over an already successful virus lineage, said Dr Stephen Griffin, a virologist at the University of Leeds.

“It’s not so much the exact mutations, more the number/combination,” said Dr Tom Peacock, a virologist at Imperial College London, who was the first to identify Omicron as a potential concern back in November 2021. “It’s hard to predict the effect of that many mutations appearing together – it gives the virus a bit of a ‘wildcard’ property where the sum of the parts could be worse than the parts individually.

“It is definitely a potential candidate for what comes after BA.5. Failing that, it’s probably the sort of thing we’ll have come along next, ie a ‘variant of a variant’.”

Even if it does not take off in other countries, its growth in India suggests it is likely to be an issue there, at the very least, Peacock added. “It’s clearly growing pretty well in India, but India hasn’t got much BA.5, and it is still very unclear how well it fares against [that].”

Griffin cited it as yet another example of the virus’s impressive capacity to tolerate changes in its spike protein – the part it uses to infect cells, and which most Covid vaccines are based on.

“This time last year, many were convinced that Delta represented an evolutionary pinnacle for the virus, but the emergence of Omicron and the vast increase in variability and antibody evasiveness is a sign that we cannot as a population follow an influenza-like plan to keep pace with viral evolution,” said Griffin.

In addition to vaccines, longer-term plans should include variant-agnostic measures to prevent infections and reinfections. “This includes creating infection-resilient environments through improved ventilation, filtration, or sterilisation of indoor air, sensible reprovision of lateral flow tests, and appropriate and supported isolation periods that will actually reduce ongoing transmission,” he said.

Meanwhile, the government’s public accounts committee has called on health officials to do more to reach people who are still unvaccinated, and therefore at greater risk of becoming hospitalised or dying as a result of Covid-19.

In a report on the rollout of the Covid-19 vaccine programme, it said NHS England and the UK Health Security Agency should urgently evaluate which approaches were most effective for increasing uptake, and support local areas to deploy them.

At the end of May 2022, 2.98 million adults in England remained unvaccinated, with a further 1.5 million having only one dose of a Covid-19 vaccine. Many unvaccinated people are young city-dwellers, but there has also been particularly low uptake among pregnant women, the report said.

“Despite work to date, low vaccination rates persist in many vulnerable groups and fresh approaches are needed to reach them,” said said Dame Meg Hillier, who chairs the public accounts committee.