A decline in case numbers comes as restrictions are relaxed. There are some important unknowns, however, just around the corner.
Auckland is out of lockdown, there are 17 days to Christmas and that curve looks very good. After five weeks of three-figure daily counts, three of the last six days have brought fewer than 100 new community cases of Covid-19. Both three-day and seven-day averages suggest we’ve hit the crest, and now we’re sledging delightedly, festively downhill.
The spread of the coronavirus has been stymied by a pincer movement: the restrictions of alert level three in Auckland combined with high levels of vaccination. As of yesterday, 93% of the eligible population aged 12 and over had received at least one dose, with 88% double-dosed. Across the Auckland region, where the delta outbreak is centred, 91% are now fully vaccinated.
That success is just as importantly reflected in hospitalisations. Yesterday’s update recorded 66 people in hospital, the lowest since November 4. There were seven people in ICU or HDU, down from a peak of 11 last month. The picture, as the traffic light system beds in, looks rosier than it has for some time.
But – yes, of course, there is a but coming – it’s no time to wrap a Mission Accomplished banner on our frigate. “It’s definitely good news,” said Michael Plank, a professor in the School of Mathematics and Statistics at the University of Canterbury. Modelling by Te Pūnaha Matatini, for which Plank is principal investigator, had projected the size and timing of the peak, but the drop since that peak has been sharper than anticipated. “Moving into the traffic light system I think that puts us into a reasonably strong position, with case numbers dropping and hospital numbers at a reasonably manageable level. But it’s really quite unpredictable what happens next.”
The critical next question concerns the impact of the traffic light system, which launched last Friday, bringing considerable relaxation of the rules around hospitality and social gatherings. We’ll need to wait for those answers. It wouldn’t be until at least 10 days in – so next Monday, December 13 – that any growth in case numbers would be discernible, said Plank.
The reproduction rate
The latest case numbers suggested the reproduction rate, or R number, had fallen to somewhere between 0.8 and 0.9, reckoned Plank. (An R number of 0.8 means every five infected people pass the virus on to four between them; an R number of 1.5 would mean every two people pass it on to another three.) “It has been declining fairly consistently over the past couple of months almost,” said Plank. “We think that is the effect of increased vaccination rates, just making it harder for the virus to spread.”
What can TPM modelling tell us about how that might change under the traffic light system? “The model suggests that if we went back to life completely as normal, as level one – if we forgot about masks, forgot about everything – we’d expect the R number to be in the order of 1.6. That would mean quite rapid case growth. Obviously we do have masks, we have vaccine passes, we’ve got gathering limits under the red setting, so those things will bring the R number down. But it’s quite tricky to predict exactly where it will land. I would expect it would be somewhere between 1 and 1.5. There’s quite a big difference there in terms of how quickly cases would grow, from reasonably stable to cases growing quite sharply.”
It’s complicated further by the arrival of summer holidays. Schools breaking up “will possibly give us a temporary reprieve”, but once they return, workplaces regroup and the weather cools, that brings with it risk of a “more sustained rise in cases”, said Plank.
Europe stands as a warning of the way winter heralds a surge in infections. “We do have a few aces up our sleeves, though. We’re starting with a booster programme now, which gives us a headstart relative to countries in Europe. I think we need a really strong push on boosters now to use the time we have over the summer to really get that programme out widely.” On top of that, children aged 5-11 are likely soon to be able to be vaccinated. “That provides another layer of protection.”
The other imminent change is the lifting of the hard border around Tāmaki Makaurau. Just as we begin to get a sense of how the traffic light system has influenced case numbers, on December 15 Aucklanders will be free to travel – if double vaccinated or having returned a negative test – to all corners of the country. “It’s difficult to relate the travel variables with the R number,” said Plank. While cases move around the country, that doesn’t directly change the spread.
Most concerningly, Covid could make its way into pockets of Aotearoa where some of the most vulnerable people live, including communities with high Māori populations, and where health services are thinner on the ground and further away. “The biggest concern as people start to move around the country more is if the virus finds its way into parts of the community with low vaccination rates it could start a dangerous outbreak,” said Plank.
The omicron factor
As New Zealand prepares to enjoy summer, meanwhile, an amorphous, ominous storm cloud has appeared on the horizon, in the form of the omicron variant. Could that blow the trends, models and expectations out of the water were it to penetrate New Zealand’s defences?
“It’s very concerning,” said Plank, adding a note of caution: “It’s still early days in terms of trying to model how omicron could spread in New Zealand. We still don’t really know how well existing vaccines will work. We don’t know the nature of omicron in terms of how transmissible it is and how well it can bypass immunity and the severity of the disease. What we do know is that it appears to be able to spread much faster than delta. That’s certainly true in South Africa. It looks like it’s starting to be the case in the UK as well.”
The sheer speed of transmission meant that “you are potentially going to be looking a very large number of cases – even a small number of infections can cause a large problem for the health system,” he said. “Personally I think we need to do all we can to delay the arrival of omicron in New Zealand.” We have “a few weeks of breathing space”, before border restrictions are relaxed further. “We’ll know a lot more by that time … Maybe things will look different in a month, but from what we know at the moment it certainly looks concerning.”
Speaking in parliamentary question time yesterday, Jacinda Ardern said the decline in the key numbers was “heartening”, but the government was at this point keeping large parts of the country in the red traffic light setting because, informed by examples around the world, they would continue to “deliberately take a cautious approach”.