Geographical allocation of positive COVID-19 cases
Published 16 November 2020
Applies to England
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Dr Yvonne Doyle, Medical Director at Public Health England, said:
We have updated the way we record the location of people who test positive for coronavirus to prioritise addresses given at point of testing, rather than details registered on the NHS database.
This better reflects the distribution of positive cases in recent weeks and months, particularly among younger people of university age who may not have yet registered with a GP at their term-time address.
This has not affected any decision about local and national restrictions, which take into account a wider range of evidence.
Background
The change comes into effect today (16 November) and will be reflected in today’s dashboard update which is slightly delayed due to data processing.
NHS Test and Trace collects location data at the point of testing. This is retained in the system even if an individual’s GP records contain a different postcode.
These addresses may differ for reasons including people moving home, students going to university or even people relocating for short periods due to work commitments.
Since 13 October, local authorities have been able to see data based on both GP-registered addresses and those given at testing to provide full clarity on the situation in their area.
Until the end of August, approximately 4% of positive laboratory-confirmed coronavirus cases had given an address at point of testing that was in a different local authority compared to the permanent address registered on the NHS database (Summary Care Record).
Between 1 September and 12 October, Public Health England (PHE) analysis found this had risen to 12% of cases, driven mostly by younger people aged 17 to 21, consistent with the relocation of many students across the UK. By week 44 (26 October to 2 November), this had decreased again to 6.6%.
The vast majority of local authorities have seen little change in how cases are allocated as a result of this change. In week 41, (5 to 11 October), one of the weeks in which counts were most affected, recalculated incidence rates are higher than 10 per 100,000 in 23 local authorities. Two local authorities, Newcastle and Nottingham, have more noticeable increases of more than 200 cases per 100,000 population. In 120 local authorities, the address reallocation results in a fall in rates greater than 10, although no area decreases by more than 35 cases per 100,000 population.
PHE and the Joint Biosecurity Centre (JBC) have analysed any potential impact on decisions about local and national restrictions. The conclusion is that recording location based on the NHS database has not affected any such decisions which take into account a wider range of evidence, including the test positivity rate, an assessment of the local response and plans, and the trend of other metrics, such as healthcare activity and mortality are all considered.
This issue would not have affected contact tracing by NHS Test and Trace, as most people are contacted by email or text message from the details provided at the time of testing.