Coronavirus sub-variant ‘Centaurus’ spreads across India and parts of Europe

An Omicron sub-variant that is spreading rapidly in India and has been detected in several European countries may be better than other coronavirus strains at overcoming immunity provided by prior infection and vaccines.

BA.2.75, which has been nicknamed Centaurus, appeared to have mutated in a way that could indicate “major immune escape”, said the World Health Organization’s chief scientist Soumya Swaminathan, adding that it showed a “clear growth advantage” over other variants in India. Global health authorities issued a similar warning when the highly mutated Omicron variant emerged late last year.

The strain has been detected in a number of countries including Germany, Japan, the UK and the US. Dutch health authorities on Wednesday became the latest to announce they had detected the strain.

“We now have 169 sequences from 12 countries — the increase observed is despite the reduction of [samples] in [genomic sequencing platform] Gisaid,” said Swaminathan.

She stressed that it still was not known whether the variant was more severe, more transmissible and immune evasive, or only the latter. “Every future variant will have these advantages if it has to out compete previous strains,” she said. A growth advantage could be due to intrinsic qualities of the virus or to changes in population immunity.

The variant was first identified in India and the nickname Centaurus later circulated on Twitter. Global health authorities were not involved in providing a name. The WHO, which oversees the process, named Omicron and would not provide another for a sub-variant.

The strain’s advance comes as health authorities contend with a resurgence of the pandemic, largely fuelled by the BA.5 Omicron sub-variant. The WHO said it had seen an “increase in trend” in case reports over the past week, something that was “concerning” given the reduction in global coronavirus testing.

European health authorities this week recommended wider eligibility for second boosters, saying those over 60 and those who are immunocompromised should get one. US authorities had previously issued a similar call.

“Prudent governments are really looking at their plans,” said Mike Ryan, the WHO’s executive director for health emergencies, referring to authorities’ preparations for an expected surge in infections later this year.

Governments have also taken the unusual step of opening up second boosters to broader parts of their populations before Omicron-variant vaccines become available later this year.

The deployment of Omicron-variant shots has been backed by EU and US regulators as well as the WHO, as it appears likely that coronavirus will continue to evolve.

Peter English, a retired consultant in public health, said the spread of the variant called for caution.

“The virus is still transmitting, very widely. In doing so it is mutating. Some variants are fitter than previous variants — intrinsically more transmissible and/or better able to evade immune responses,” he said. “Immunity lasts less time than we had hoped, so people can be infected repeatedly, with cumulative damage.”

Current vaccines are modelled on the strain of coronavirus as it first emerged in Wuhan, China, more than two years ago. They continue to retain high levels of protection against severe disease, but their efficacy is waning as more time lapses from the first rounds of vaccinations and the virus continues to evolve.

The WHO’s Ryan compared the protection afforded by vaccines against Covid to a wall protecting a castle. “It gets weak, it gets cracks, there are holes in the wall,” he said, adding that immunological memory “fades over time”.