Otago University epidemiologist Professor Michael Baker says an Omicron outbreak in New Zealand isn't a question of if, but when. He answers five key questions.
Why is Omicron something to worry about?
I think the main problem is its ability to drive widespread, rapid transmission, infecting large numbers of people in a very short period – and there are two reasons for this.
Firstly, the Omicron variant is highly infectious. Some of this advantage comes from that the fact that it appears to be inherently very transmissible.
I have not seen a basic reproduction number quoted for Omicron, partly because it's hitting a world that has two years of accumulated immunity.
Its high infectivity also comes from its ability to evade some of the immune protection that people have from prior infections, as well as that from vaccination.
There's some speculation that it's not necessarily inherently more infectious than Delta, which suggests we might finish up with two variants co-circulating.
Secondly, it appears to have a shorter incubation period than previous variants, allowing it to spread rapidly and giving less opportunity for tracing, testing and isolating infected contacts.
Omicron may be showing us what we can expect to see in the future with new variants gaining their evolutionary advantage by evading immunity – allowing them to infect a high proportion of the population.
This is how new strains of influenza keep replacing older ones.
When can we expect an Omicron outbreak here?
In the past, I would never have said it was inevitable that a new variant would arrive here, but I think Omicron is so infectious that it will be hard to keep it out long-term.
We have carried out research with Australian colleagues to look at the frequency of border failures. In the past, we've had about one border failure per 100 infected people entering MIQ in New Zealand - or an average of one per 167 people across New Zealand and Australia.
Only a minority of these failure triggered significant outbreaks, but it gives us an idea about the leakiness of border controls and how risk rises in proportion to the number of infected people arriving.
Having much more than five to 10 infected travellers per day will result in a high risk of border failure in the next few weeks.
In the last 10 days we have had more than 250 people arriving in MIQ and testing positive for Covid-19. Most will be infected with the Omicron variant.
This high "force of infection" overseas will also increase the risk of infection in air crews, and probably ship crews as well.
This all reminds us that all borders and every defence is permeable: Delta managed to get into virtually every country on Earth and Omicron looks even harder to control.
Our border defences use a multi-barrier approach to health protection. Like Swiss cheese, all of these barriers are porous so we need all of them to work as well as possible. The first barrier is to minimise the number of infected people arriving in MIQ.
To keep this barrier working we need to rapidly turn down the tap of infected people arriving into NZ.
If we don't do this, we will rapidly see Omicron cases overwhelm MIQ resulting in a border failure. Without a rapid response, this failure is likely in the next few days or weeks.
What would an Omicron outbreak look like?
It could look a lot like the Delta introduction in August last year, except it would spread far more rapidly.
We may just suddenly become aware of a community case of Omicron infection, and it'll probably again be in Auckland, as that's where people are flying into.
We'd see one case, and we'd know it'd probably be the tip of a large iceberg of cases.
The "tight-suppression" approach we are using has been working extremely well at dampening down the current Delta variant outbreak. And while it would slow Omicron, it wouldn't stop widespread transmission.
I think we'd almost certainly see what's happening in New South Wales and Victoria – which have each been recording tens of thousands of new cases each day – because they're very similar in terms of population make-up and vaccination coverage to us.
That's unless we took very vigorous action to slow it down.
Are we prepared enough right now?
No. Arguably nowhere is really prepared for an Omicron outbreak. However, we need to get far better prepared than we are now.
Our test and trace system would be one area that would be rapidly swamped.
Even though capacity for PCR testing has been increased to around 60,000 tests a day, other parts of the system would not be able to keep up. The ability to swab large numbers of people in the community and follow up contacts could become overwhelmed.
It's also important to point out that, while you'd have massive surge in demand, this wouldn't be evenly distributed across the country.
The other thing, of course, is a lot of people will turn up at GP clinics, or hospitals outside of hours.
We can expect the ambulance system to be quickly overwhelmed, and also staff shortages – which are factors that have now been well documented in the UK and Australian healthcare systems.
These staff shortages might also start to interfere with other essential infrastructure such as food distribution.
What pre-emptive measures should Government be taking?
The number one priority should be turning down the tap on the number of cases arriving into New Zealand.
That means doing a detailed analysis of where the cases are coming from, and if we're getting more than a certain proportion from some places, limiting travel from there.
If we can push the number of active border cases down to five or 10 each day, then we've got some chance in delaying Omicron's arrival.
While we wouldn't want to stop all flights coming in, we do need to bring volumes down, and explain to all New Zealanders that this is the best we can manage to keep Omicron out for a period, at least until March.
It's a calculated move, but it may buy us time to plan and implement measures to minimise the health impact from the Omicron variant if and when it spreads widely in NZ. This is where "flattening the curve" to slow transmission really makes sense.
This planning can include a risk assessment on this variant and learning from best practice overseas.
Key prevention measures are giving every adult New Zealander a chance to get a booster, and to give every school-aged child a chance to get double-vaccinated.
We really need to review and expand our ability to manage lots of sick people in the community. If we can provide capacity for a "hospital at home" approach could ensure people are adequately cared for in that environment.
Obviously, hospitals will likely see a large increase in admissions, but the evidence is that this might be largely manageable if we can support people in their own homes.
Elsewhere, the Government could keep building up supplementary testing capacity with rapid antigen tests.
It would be good to strengthen the pharmacy network and the supplies it receives, as pharmacies do have the capacity to administer tests, add this information into the national Covid-19 surveillance system, and to also give advice on what medications to take if someone does test positive.
We also need a national mask strategy, so people know a lot more about what types of masks they should be wearing, and when they should be using them.
The two main areas the public should be thinking about, meanwhile, are how to minimise their risk from Covid-19 infection, and how to manage at home if they get infected.
Getting vaccinated and boosted is obviously the key priority. Using effective masks will help to prevent infection has the advantage of working on all variants.
People who are particularly vulnerable may need to start using higher quality N95 style masks routinely when indoors with other people.
The public will need a lot of practical advice and support about how to manage with Covid-19 infection at home.
This will need to cover such areas as: recognising when they are sick and need to get additional help or call an ambulance; essential supplies they should have including pharmaceuticals to manage symptoms; guidance to minimise transmission in the household, if there are other people living there; and arrangements for others to check on them if they get sick at home, particularly if living alone.
New Zealand is one of the few countries able to delay entry of Omicron. We should use this strategic advantage well.