Australia and NZ's risk profiles are different from pretty much anywhere else in the world right now. On that level, it's not a particularly reckless move.
That said, I understand the hesitation that a lot of people, particularly from NZ have. Our positions (both NZ and Australia's) have been hard earned, and one major slip up could make it all count for nothing.
Fiji hasn't had a single covid case in the wild in a year, with all our covid patients being detected in quarantine and isolated until recovery.
No bubble with us though. The Aussies get it first.
That said, my point was that opening NZ up to Australia (and vice versa) is a very different scenario to opening up to eg the US, France or the UK.
So the pandemic will end for NZ the same way it will for every other country: when everyone has had a chance to be vaccinated. That should be some time this year for NZ. Some other countries will get there first, but the timing depends entirely on vaccine supply and uptake, and has nothing to do with how far COVID has spread through the population.
If that happens before a mutation spreads which renders the vaccines useless. And, seeing the pace at which vaccination is progressing in poorer countries, I'm not really optimistic about that. On the other hand, there is still hope that the vaccine will at least keep you from getting seriously sick if you get infected with a vaccine-resistant strain...
See also https://www.theguardian.com/world/2021/apr/06/global-rollout...
Even if the case numbers (~140M worldwide) were underreported by 80% (i.e. that there are five times as many cases as we actually know about), it still would just amount to only roughly 10% of all people worldwide.
It's been reported that more than half of the UK population now has Covid antibodies, either through recent infection or through vaccination:
https://www.theguardian.com/world/2021/mar/30/about-50-of-pe...
https://www.sanquin.nl/over-sanquin/nieuws/2021/03/corona-an...
Interestingly, the percentage is higher (26%) in the southern provinces of Limburg and Noord-Brabant, which were hit hardest by the first wave due to a combination of Carnival (only celebrated in those areas) and differently timed February school vacations.
Some of this probably is a vaccination effect- they've noticed that women were more likely to have antibodies than men, and more of the female donors were healthcare workers.
Back in October - i.e. before the massive second wave most of the world saw over the winter - the WHO estimated that around 10% of the world's population had been infected with COVID [2]. It wouldn't be surprising at all if the number were substantially higher now.
The idea that case numbers are underreported by only 80% worldwide is extremely generous. That's pretty close to the CDC's estimate for the US (1 in 4.6) [3], and the US has per capita one of the most aggressive testing regimens in the world [4].
[1] https://covid19-projections.com/infections/us-sd
[2] https://www.usnews.com/news/health-news/articles/2020-10-05/...
[3] https://www.cdc.gov/coronavirus/2019-ncov/cases-updates/burd...
[4] https://www.statista.com/statistics/1104645/covid19-testing-...
I didn't say that a part of the world has natural immunity, just said that nobody has natural immunity in NZ, which is where we were a year ago.
Besides that, negligible in which context? Many countries have already had double digit % of their population having had a COVID infection which might not be enough, but it's also not entirely negligible, since it means that any new wave would be less steep than the wave beforehand.
a) I know of quite a few families where one or two members tested positive, but others did not. If the virus spreads as easily as we think, then it's extremely unlikely that all of the family didn't have it at some point.
b) Most of the people I know who have tested positive have had mild symptoms, I expect there are a lot of people who were asymptomatic or had very mild symptoms and just thought it was a cold.
c) After 5 months of lockdown, most people have given up following the guidance about not meeting up privately and wearing masks inside if you do, but the case numbers haven't gone out of control.
This also doesn't take into account vacinnations. We are at around 14% so far, so I wouldn't be surprised if total immunity is close to 50%.