Earlier this week I presented to some government officials about technology for contact tracing from an outside perspective. I’m not in the health/govt system, and so can only provide comments based on the evidence that I can find from OIA requests and publicly published data sources. There is a reasonable chance that my perception of what is happening is different to what is actually happening in the health system and in the contact tracing / case investigation process, so take my comments with a grain of salt.
The question that I’ve been asked is “how could technology
better support contact tracing [as the case numbers increase and we head towards
a new public health strategy]?”
Requirements
An engineer starts with the requirements – firstly what is it that we are
wanting to achieve? We need to physically isolate infected persons to cut off
the chains of transmission. To do that, we need to know who an infected person
has been physically proximate to. Since people are sometimes around strangers or
can’t remember who they were near, we can use location as a proxy.
What else informs the requirements? The overall strategy is
important – what is your tolerance for false positives (isolating a person who
doesn’t have COVID-19) and false negatives (leaving a person with COVID-19 in
the community)? The context is changing as we move to there being more daily
cases while opening up the country as we reach high vaccination rates.
Time appears to be the most important factor – time-to-isolation
is modelled to be one of the strongest influencers on the reproductive rate of
the virus. But what are requirements need to be considered? Which might be
dealbreakers? Flexibility? Equity? Interoperability? Privacy? Social Licence? The
technology is theoretically available to track every person with a cellphone in
real-time, but that would strongly infringe on the public’s rights. We cannot optimise
only for one factor.
Automation is key to speeding things up, which relies on a
good understanding of how processes are deployed today. To help us with this, let’s
split the tools for better contact tracing into two categories: contact tracing
process automation (i.e. “business processes”) and consumer-facing digital
contact tracing (i.e. “the app”).
Business Processes
The contact tracing processes are opaque to the outside world. Even after all
this time the public does not have a great understanding of exactly how contact
tracing works and what the protocols look like. In addition to this, we don’t know
how much deviation there is between the protocols and the real-world case
investigation process. How much can we speed things up without losing too much
accuracy, noting that we are likely already losing accuracy because humans are
not perfect?
It appears to me that the capacity constraints in the
contact tracing system are critical now. We have seen this in recent days with statements
that prioritisation of locations of interest by risk-level is now necessary.
Even where digital contact tracing tools are providing data from the case, it
is hitting the bottleneck of human contact tracers making phone calls. We could
try to add capacity to the system, but even there we find bottlenecks. Training
is an important part of adding more contact tracers, but there are people who are
volunteering to become contact tracers who seemingly can’t get training right
now.
I am not advocating for a fully automated contact tracing
system – the human element is very important for making people feel at ease and
to ensure that their needs are met, especially at the point when a case is
first notified that they have tested positive. But there are parts of the
system that could be automated. For example, right now a contact tracer has to talk
a case through the process of going into the NZ COVID Tracer app and typing in
a code to upload their diary to the contact tracers. In some other
jurisdictions, this is sent out as a text with a link to further instructions,
which takes up less contact tracer time.
To my understanding, the contact tracing / case
investigation protocols are currently being redeveloped. I think part of this
needs to include an honest look at which steps could be automated, in consultation
with clinical advice, to make contact tracing more efficient and therefore
scalable.
Consumer Digital Contact Tracing
We can look at the digital contact tracing tools that we try to put in the hands
of all New Zealanders. When we look overseas, our tools are pretty much at
parity – more jurisdictions are moving towards contact tracing records (e.g. QR
codes) and moving away from Bluetooth (because they can’t get participation
rates up high enough). But there isn’t a lot of use of other technologies like
GPS or cell tower geolocation.
But instead of looking at the other technologies (which
require a different trade-off with other factors), we should look at the
technologies we already have. We are not using Bluetooth Tracing (BT) nearly as
much as we could or should. There is something happening in the contact tracing
/ case investigation process that we need to understand.
The public is able to see the number of BT keys that are
uploaded to the MOH server, which correspond to individual cases who have provided
data (noting that multiple keys may relate to the same person). Between
17 August and 1 October 2021, there were 6 devices providing BT keys, and
11 contacts were notified based on those keys. There were over a thousand cases
over that time period.
We have seen more keys being uploaded in October, but still
not enough given that there are around a hundred new cases a day. We have a relatively
high uptake/participation in BT relative to other jurisdictions. I was on a
videocall recently that included representatives of a number of European countries,
and I asked what their uptake rates were.
After the provisos about how hard it is to measure uptake
rate, they all landed somewhere around 20-25% of the adult population. They
thought this was great and they were finding contacts and saving lives. In New
Zealand, we currently have devices equivalent to 55-60% of the adult population
participating in BT each day. They were amazed that we had such a high
participation rate. I was amazed that we were getting so little data out of it.
We also don’t track the data all the way through the process
– we currently don’t know how many people got a test because they got a NZ
COVID Tracer alert of any type. So we know how many people were notified that
they are a contact through the app, but lose the trail after that [note that I think the protocols ask for whether or not a positive case has received an app alert]. We need
better metrics for understanding the usefulness of digital contact tracing before
we can really make decisions about whether it is useful or not.
There is also concern that the changing approach in only releasing
high-risk locations of interest (which are related to the QR codes rather than
BT) will also change the comprehensiveness of alerts that are sent through NZ
COVID Tracer, and how this might affect uptake/participation. This may help
with avoiding a high rate of false positives (aka the “pingdemic” seen in the
UK), but is also at odds with most users’ conception of the purpose and
function of the app.
Conclusion
So could we use technology to better support contact tracing? Yes, but not
by using new technologies to collect more data. It’s about using the tools we
already have more effectively, rather than trying to add more tools that may not
add much benefit at great cost. It’s about how the data that is already being
collected is being used, and how we can measure that to understand its utility.
And it’s about supporting human contact tracers to be the most effective they
can be, by automating the simpler and more repetitive parts of their processes.
Unfortunately we might look back and realise that this is a
conversation we should have had six months ago. But hopefully we can learn from
this experience and be better prepared going forward.
