Twenty-nine imported cases, also known as border-related cases, have been reported since April so the leaking of this latest Omicron descendant into the community was not unexpected, the Ministry of Health said.
It announced 8150 new community cases of Covid-19 today, 368 cases in hospital including 11 in intensive care, and a further 11 virus-related deaths, including a child aged under 10.
Dr David Welch, senior lecturer at the University of Auckland's school of computer science, said the new subvariant in the community is not a cause for panic but a reminder the pandemic was not over and should be taken seriously.
"It's not a game-changer, it's not like Omicron was where all of a sudden we're going to get a massive peak [in cases] because of it."
BA.2.12.1 has become the dominant variant in the United States, making up around 58 per cent of new cases between May 15 and 21, according to the Centres for Disease Control and Prevention.
The New York Times said the subvariant, a form of BA.2, spreads more rapidly than previous versions of Omicron but there is no indication it caused more severe disease than earlier forms.
The vast majority of recently sequenced cases in New Zealand continue to be the Omicron BA.2 subvariant.
A weekly report from the World Health Organisation published on May 18 said BA.4, BA.5 and BA.2.12.1 had become more prevalent in the countries they were first detected - South Africa and the US, respectively - and spread to other countries.
As of May 18, BA.4 had been detected in 20 countries, BA.5 in 19 countries and BA.2.12.1 had been detected in 38 countries.
University of Otago evolutionary virologist Dr Jemma Geoghegan said BA.2.12.1 had around a 10 per cent "growth advantage" over B.A.2, which meant it could infect people more efficiently.
Anything with a growth advantage could be expected to replace previous variants circulating in the community and could lead to an increase in cases. However, we were still learning about how much immune protection New Zealand had as a population that experienced a big BA.2 wave and how long that protection will last.
Welch said the new subvariant was expected to become the dominant variant within, perhaps, a few months.
"[It probably has] a similar sort of growth advantage that BA.2 had over B.A1, I would say; that's a lot less than the difference between Delta and Omicron, for example."
Welch noted New Zealand was in a different situation from other countries in that we had a large BA.2 outbreak while many other countries didn't and BA.2 could provide New Zealanders with better immune protection against the latest variant.
The best thing people could do was get themselves and their children vaccinated and boosted when possible, wear masks and test if they had symptoms, he said.
Dr David Welch is a senior lecturer at the University of Auckland's Centre for Computational Evolution and School of Computer Science. Photo / Jed Bradley
"It's not [a] panic station. I don't think anyone is going to be calling for a change in the alert level or anything like that. But it's another reminder this pandemic is far from over and while this disease is here with us, we need to take it seriously."
