On the eve of New Zealand, there were 146 new cases of Covid-19 in the community migrating to a new signaling system.Video / NZ Herald
Why does the number of Covid-19 cases in Auckland appear to be declining? And what trends can you expect to see after cities and other countries move to traffic light ratings? Michael Plank, Professor Covid-19 Modeler of Te Pūnaha Matatini, answers five simple questions.
The number of cases in Auckland is declining. How important is this decline in the context of broader outbreaks?
I don’t call it a sharp drop. I think the number of cases has leveled off, but it may be starting to decline gradually.
The numbers are bouncing up and down a bit, but the trend is starting to appear to be declining.
It comes down to a combination of two things.
One is vaccination and the other is that there are still restrictions in Auckland. That is, many places are still closed and many people work from home.
Vaccines, in a sense, mean that the virus reaches a dead end or it becomes difficult to find a new sensitive host.
At the same time, if we remove the restrictions and masks and bring them back to life as usual, I think the virus can still spread fairly quickly.
At this point, it’s great that vaccines are winning, cases are leveling off and starting to decline.
However, it is trying to significantly ease the limitations of traffic light systems.
What about the case number in a fictitious scenario where Auckland restrictions remain in place?
It will gradually bring the R number as we are still vaccinated people [the average number of cases caused by a single infection] under.
At the moment it is just below 1 and its value will decrease over time and the rate of decrease in cases will be steep.
If it stays that way, we will return to exclusion for long enough.
But that’s probably not realistic, given that people are tired of being blocked and can’t keep it forever.
So what can we expect when the traffic light system works?
The model currently suggests that the restrictions in place in Auckland have reduced the R number by about 40%.
This suggests that if all restrictions are removed, the R number will rise to about 1.5.
However, I don’t intend to do this because I know I need a mask. In addition, measures such as capacity limitation have been taken in the new signal system.
And of course, there is also a vaccine pass. I think the R number will eventually be between 1 and 1.5, but where to land in that range is actually based on speculation.
However, there is a big difference between the two. At 1.5, the case numbers increase fairly rapidly, but near 1, the case numbers are fairly flat.
This is very important in deciding what will happen next when it occurs.
And what about nationwide incidents?
Many of them depend on people’s reactions.
In the UK, for example, all restrictions have been removed, but many people wear masks and continue to work from home.
There are many preventative actions that are stuck, even if they are no longer needed.
We know that wearing a mask can have a huge impact, and that will be a factor here as well.
If everyone goes out to the party at the moment the restrictions are relaxed, it can spike in some cases.
But if people remain a little more cautious, it helps reduce the number of cases.
You should also consider that things are a little different during the summer.
Obviously, we are changing a lot at once – and the opening of Auckland’s border will lead to more incidents across the country.
However, there are times when schools are closed, many workplaces are closed, and people are outdoors. This makes it difficult for the virus to spread.
So you can’t just conclude that the virus doesn’t spread, but the case numbers may be choppy and do nothing dramatic during the summer.
But when school returns, things can change and incidents can increase rapidly again.
It will make a difference if you start vaccination of children aged 5 to 11 years.
What other trends are you looking at?
Whether the virus has succeeded in establishing a significant outbreak in other parts of the country.
When Auckland’s borders are lifted, you’ll see incidents scattered all over the country, which is unavoidable, but it’s interesting to see if they can be established.
We know that areas with low immunization rates are at high risk, and you may find it really very difficult for the virus to establish in those areas with high immunization.
Outbreak of Covid 19 Delta: Modelers Answer Five Important Questions About Case Trends
SourceOutbreak of Covid 19 Delta: Modelers Answer Five Important Questions About Case Trends