Minister for COVID-19 response Dr Ayesha Verrall joins Dr Ashley Bloomfield to provide an update on Covid-19 and flu. Video/Supplied
New Zealand's grappling with its second Covid-19 wave within the space of a few months. Is this our new normal and what will our future of living with the virus look like? Otago University epidemiologist Professor Michael Baker fields the five biggest questions.
We've already seen more than 1600 coronavirus-linked deaths this year, along with thousands of hospitalisations. Now that it's in our communities for good, is this essentially our future under Covid-19?
When a new virus like SARS-CoV-2 hits a naïve population, it takes a while to reach some form of equilibrium.
Effectively, we're still in a pandemic.
Flu pandemics spread rapidly, but even with these it can still take several years before the full impact is clear.
SARS-CoV-2 has been transmitting widely for two and half years but we must remember that it's only been spreading widely in New Zealand for six months.
If we look to other high-income countries, we can see that hospitalisations and deaths are still well ahead of influenza, even after nearly three years.
If the pandemic carries on at its current rate, the health burden will be very large.
Modelling shows that influenza results in about 500 deaths a year and about 2500 hospitalisations.
Just using a crude, back of the envelope calculation, Covid-19 could result in 10 times that impact – that's 5000 deaths a year and 25,000 hospitalisations.
On average, that might mean 500 admissions a week, though we would expect numbers to continue fluctuating widely.
We haven't seen hospital cases lower than 300 for about four months and now we're heading back up again.
How often each of us is likely to be infected will vary for everyone.
But if you went out to a densely-packed bar or nightclub, unmasked, every week, you're going to be heavily exposed to this virus on a regular basis.
Studies are now being published that have tracked large cohorts of people for many months showing that Covid-19 reinfections are common and can have adverse health effects each time.
Reinfections will become the norm, eventually, unless we can find better ways to prevent them.
Is our health system ready to shoulder this extra pressure year after year?
Public hospitals are almost full, all the time, because they're doing elective work when they're not doing acute work, and there's never much surplus capacity.
Once they know they're going to be in the middle of a big winter wave of Covid-19 and influenza, they obviously stop doing that elective work.
Consequently, the hospital system is rarely overwhelmed – it's just that a lot of that important work, like elective surgeries, gets deferred, which has huge consequences.
Other parts of the healthcare system like primary care are, arguably, under even more strain. They are also having to defer some non-urgent work such as important health screening.
We also have to consider the impact of long Covid on our population and health system.
Post-acute infection syndromes occur after many viral diseases and this is certainly the case with Covid-19.
There are still many important questions with long Covid about how common, severe and long-lasting it is, and whether it can be prevented with vaccination or antivirals.
Evidence suggests that long Covid is a big problem, so that makes it more important to consider greater efforts to limit infection.
If it is, then that makes it all the more important to ask: what level of effort should we be putting into limiting infection?
Otago University epidemiologist Professor Michael Baker says Covid-19 will continue to cause headaches in New Zealand - but what impact it has depends on our level of tolerance. Photo / Supplied
Part of that will be regular vaccinations. Most Kiwis have had at least three – and some four - within less than a year. In the long-term, how often are we likely to need jabs for Covid-19?
Probably the best model we have for Covid-19 vaccination is influenza.
The influenza vaccine has multiple components - currently "quadrivalent" - to cover the range of virus types and subtypes.
It is reformulated every year to take account of viral evolution.
We have our annual flu vaccination for two reasons: one is to try to keep ahead of the changing virus and the other is to top up our immunity.
For similar reasons, we might expect to get a Covid-19 booster vaccine every year, perhaps in combination with the flu vaccine.
Some particularly vulnerable groups might need additional boosters, but this need is not yet clear.
With some vaccinations, such as with the measles-mumps-rubella (MMR) vaccine, you only need two injections and that protects you for life.
With others, such as tetanus-diphtheria-pertussis it is routine to have a primary course of three doses, and then boosters at intervals throughout life.
Covid-19 appears to be in the same group, with a primary course – which we could consider to be our first two doses, plus the booster – followed by a booster each year for most of us.
However, the optimum Covid-19 vaccination strategy in the longer-term remains to be seen.
Is the virus always going to look like this?
There is always going to be evolutionary pressure on SARS-CoV-2 that helps it to keep ahead of our immunity.
We're talking about simple strands of RNA that keep making copies of themselves.
The more they do that, the more they mutate, and the more opportunity they have to produce new subvariants which are fitter and can overtake less successful ones, like BA.5 surpassed BA.2.
Viral evolution appears to be accelerated by chronic infection in immune-compromised human hosts - another reason to try to lower infection rates across the globe.
Omicron is now very fit, and it may be that we don't get an entirely new variant that comes with a new Greek letter: Pi is next in the alphabet if needed.
The future of this virus might just be more branches of the Omicron tree, as this variant appears to have an almost unlimited range of potential future configurations that could help it evade our immunity.
It's often said that Omicron isn't as dangerous as Delta, but I do think people need to consider this risk in mathematical terms.
You can have something half as virulent as the variant before it, but if it infects twice as many people, that effect is neutralised – and it's twice as dangerous if it infects four times as many.
If the virus does settle into a stable pattern, as we expect it to do over time, then we could expect to see a more incremental rate of change and fewer evolutionary leaps.
This situation could be a plus when it comes to trying to formulate vaccines against it.
Ultimately, the Holy Grail would be a vaccine that targets conserved regions of the virus that don't change, or what we'd call a pan-coronavirus vaccine.
It's still not clear if this is technically possible, but this dream vaccine would also give sterilising immunity - once you're immunised, you can't transmit the virus – and such immunity would also be long-lasting.
Is it realistic to expect that Kiwis will gradually adapt to Covid-19 by using measures like masks? Or do you expect the public will try to revert to life as it was in 2019?
Managing the pandemic is increasingly becoming a question of trade-offs and political choices.
This virus isn't going anywhere, and until it settles down into a more predictable pattern it is still a pandemic rather than an endemic threat. So we have to choose how we are going to "live with it".
One option is that we can just choose to ignore it and put up with the burden this would cause.
This could mean we'd go backwards in our mean life expectancy.
And while older people would be predominantly affected, it would also worsen health inequalities for vulnerable groups in society that have enough additional health burdens already.
The second option is that we introduce measures to reduce the daily rate of people getting infected, and all those flow-on consequences would drop proportionately.
It would come down to the three main forms of prevention we can use: vaccinate and boost to raise immunity; test and isolate to limit transmission from infected people; mask up and ventilate to reduce transmission between everyone.
Governments are there to express the will of the people about such trade-offs, just as they make policies and law to regulate alcohol, drugs, and unhealthy foods.
But the analogy I think is most useful here is driving.
We love the freedom of driving and cycling on our roads, but we hate the road toll, and have built up a huge collection of laws and codes to make this shared activity as safe as possible.
For example, we now have a very low tolerance for drunk drivers being able to injure and kill us and have rules to stop this behaviour.
When we share our roads, we try to do it safely.
Similarly, we love the freedom of getting together indoors, in often crowded, poorly ventilated environments where Covid-19 spreads easily.
But we have not yet developed and embraced the rules to make this safe.
We need a low tolerance when an infected person chooses not to isolate, and doesn't wear a mask indoors.
On average, you've got a one in 1000 chance of dying if you get Covid-19 in New Zealand today.
It's currently killing about 150 of us each week; that is about the same as the number of us being killed each year by drivers affected by alcohol and drugs.
So it might be that we decide we're just not going to tolerate that infected, un-masked person giving us Covid-19.
That's why we need Government action to make that risk as low as reasonably possible.
