If contact tracing and testing could keep up with the caseload, these records could be invaluable. They would significantly speed up the identification and isolation of close contacts, thus slowing the spread and reducing the pressure on the health system.
However, with the current caseload, it is unlikely that these benefits will accrue. The data show that most people, most of the time, are not bothering to scan in. Throughout December, daily scans were typically between 2.9 and 3.5 million, peaking at 3.96 million on 23 December. Those numbers mean far less than one scan per adult per day. Most people visit multiple locations per day. The number of individuals conscientiously using the app is not disclosed by the Ministry of Health. It might be that around one fifth of users are scanning at five locations per day. In that case, 80 per cent of users would not be regularly scanning in and will not be identified by this method.
Moreover, the number of scans has dropped significantly since Christmas, with the highest number on one day being 2.76 million on 28 January, and generally falling between 2 million and 2.6 million most days in January and February. With these figures, if the average person goes to five places per day, we can conclude digital contact tracing is less than 20 per cent effective.
A second difficulty is that, in order to work, contact tracing must identify a contact so they can isolate before passing Omicron on. We do not know how rapidly contact tracing is occurring currently, however a review of contact tracing for Omicron last year showed that only 34 per cent of cases were isolated within 96 hours, and the system failed to keep up with more than 75 active cases. Given Omicron’s incubation period is three days and there are now over 10,000 active cases, we can safely conclude that contact tracing is going to be highly ineffective against this new variant.
The Prime Minister’s case makes the point. It took 7 days from the flight where she may have been exposed to COVID-19 for her to be told about that exposure. Evidence from the CDC suggests that Omicron has an incubation period of around 3 days after exposure with patients being infectious for another 2 to 3 days after symptoms emerge. That’s 5 to 6 days after exposure in total. Thus, the Prime Minister only began isolating at the end of what would have been her infectious period had she caught COVID-19 on that flight. Her isolation was pointless. If even the Prime Minister didn’t hear about her possible exposure to the virus in time to stop further infection, what hope do the rest of us have?