COVID-19: What is the new XBB variant now in New Zealand and are scientists concerned?

XBB was detected this week.
XBB was detected this week. Photo credit: Getty Images

While New Zealand moves on from the peak of the Omicron COVID-19 outbreak, a new variant has arrived on the country's shores.

The strain, XBB, was detected and reported by the Institute of Environmental Science and Research this week. It is another Omicron subvariant. 

XBB was first reported in India in August and has since spread to multiple other countries including the US and Singapore.

What's different about XBB?

XBB differed from other Omicron subvariants because it's a recombinant strain, meaning it has combined genes from earlier versions of the coronavirus.

Experts have said XBB would likely be more transmissible than previous Omicron subvariants, which could be a factor in Singapore's rising case numbers. The country reported a seven-day rolling average of 8195 new daily infections on Wednesday - up from 7499 the previous week. 

Last week, XBB caused Singapore to take "steps to ensure that our healthcare capacity remains protected". 

"This XBB is a recombinant of two BA.2 sublineages and, in particular, BA.2.10.1 and BA.2.75," said World Health Organization COVID-19 technical lead Maria van Kerkhove. 

"We do know that this recombinant has a significant growth advantage - all of the subvariants of Omicron are showing increased transmissibility and properties of immune escape.

"With this XBB recombinant, we have one study… that is analysing antibody escape and is showing significant immune evasion," Dr van Kerkove said.

XBB, as well as other subvariants including BQ1.1 - which was detected in New Zealand last week - "are going to have a greater ability to reinfect people than what is currently circulating", Imperial College London virologist Tom Peacock told The Washington Post.

Doctors continued to strongly recommend getting vaccinated and boosted against COVID-19 for maximum protection against emerging variants - including XBB.

"We don't see a change in severity yet and our vaccines remain effective, but we have to remain vigilant," Dr van Kerkove said.

As of Tuesday, 612,500 New Zealanders had received a second COVID-19 booster jab and 2.7 million have had three doses. 

Boosters specifically designed to fend off Omicron and its subvariants could also be available in New Zealand soon after Pfizer made an application to MedSafe for provisional approval of its bivalent COVID-19 vaccine. 

"We're still waiting for data on efficacy but there is data that suggests there's a modest increase in neutralising antibody levels against the Omicron variants in particular," immunologist James Ussher told the NZ Herald.

"Given that BA.1 has now virtually disappeared, we're now looking at descendants of BA.2, BA.4 and BA.5 - or the ones that are circulating globally today," said Ussher, from the University of Otago.

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