What do we know about the UK variant involved in the latest Covid-19 community cases? Science reporter Jamie Morton explains.
First off, what is a variant?
Viruses constantly change through mutation and new variants are expected to occur over time, sometimes vanishing, while at other times persisting.
The three main variants of the SARS-CoV-2 coronavirus circulating around the world are known as the UK (B.1.1.7), South Africa (B.1.351) and Brazil (P.1) variants.
The South Africa variant was involved in the recent Northland scare and infections within Auckland's now-closed Pullman Hotel MIQ facility, while cases of the UK variant have also been increasingly turning up at our borders.
The latest three community cases have all been confirmed as the UK variant, which was first identified late last year.
What's the concern with this particular variant?
It's known to spread more easily and quickly than other variants.
Last month, experts in the UK also reported that this variant may be associated with an increased risk of death compared to other variant viruses, but more studies were needed to confirm this finding.
Professor Neil Ferguson, of the British Government's virus advisory committee, said the latest data showed up to 13 in 1000 people aged 60 who contract the variant strain could die, compared with 10 in 1000 who caught the original variant.
"It is a realistic possibility that the new UK variant increases the risk of death, but there is considerable remaining uncertainty," Ferguson told ITV.
Te Punaha Matatini and Canterbury University Covid-19 modeller Professor Michael Plank last month said the number of new cases per infected person - the so-called "R number" was 40 to 70 per cent higher than the original strain.
"This is a serious concern because of the potential for explosive exponential growth."
What does it mean for New Zealand?
Plank said the variants were important here, because the risk of one leaking through our border defences is higher, given there was a greater chance of a quarantine worker getting infected.
"If there is a community outbreak of the new variant, it will spread much faster," he said.
"An increase of 50 per cent per cent in the transmission rate might not sound like a lot but can quickly lead to much bigger outbreaks because it gets compounded by exponential growth.
"For example, the original strain of Covid-19 would typically infect about 160 cases after five links in the chain, whereas the new variant will typically infect about 1000 cases in the same time."
He said a community outbreak would likely also require tougher restrictions to bring it under control.
"All the tools we have developed to fight Covid-19 will still be effective, but we will need to use more of them," he said.
"Alert level 3 was effective in containing the August outbreak, but it's likely we would need to use level 4 to have the same effect on the new variant. And restrictions might need to be in place for longer to eliminate the virus."
Plank believed that beefing up border controls to keep the virus out would be a good idea.
"The Government has introduced an additional day 0 test on arrival and a pre-flight test for people departing from the US or the UK. These are both useful additions to our border defences," he said.
"But, since the new variant is spreading rapidly around the world, it would be sensible to extend these requirements to all arrivals.
"A period of pre-travel quarantine would also help to reduce the number of cases arriving at our border."
Will the vaccines protect us from it?
There's no evidence yet to suggest the four vaccines that New Zealand has pre-purchased won't work on the variant.
Initial studies indicate the Pfizer-BioNTech vaccine - the first to be rolled out in New Zealand, among high-priority groups - and the AstraZeneca shot should still work.
Like the other shots, the Novavax and Janssen vaccines may have a slightly lower - but still relatively high - efficacy against the variant.
One early analysis of the AstraZeneca vaccine has however been shown to offer reduced protection against low to moderate infections of the South African variant - prompting South Africa to suspend its roll-out.
And some cases of the South Africa variant have been shown to share the same mutation - called E484K - with the UK variant.
In any case, Plank said the increased transmission rate meant that a higher proportion of Kiwis may need to be vaccinated to achieve population immunity against Covid-19.
- With AP