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What is contact tracing?

Contact tracing is an important part of the Welsh Government’s Test, Trace, Protect strategy. The strategy is being delivered through the NHS Wales Test, Trace, Protect service.

As soon as people start to display symptoms of coronavirus (COVID-19), they should arrange to take a test as quickly as possible whilst they and members of their household self-isolate. On receiving a positive result people are asked to support the NHS Wales Test, Trace, Protect service by reporting their recent contacts to the local contact tracer so that they can be contacted and notified to self-isolate (and take a test if they too are displaying symptoms), to help stop the spread of the virus.

It may not be possible to trace all individuals referred to the contact tracing service. For various reasons contact details will not have been provided for some individuals and others may not have responded to calls, texts or emails from tracing teams. The proportion of positive cases that were eligible for follow-up and that were reached only include those cases that were successfully reached but does not include those cases where local tracers have made an attempt, but failed, to contact.

The data in this release is management information collected as part of the contact tracing process. The figures reflect the data recorded in the contact tracing system and not any contact tracing activity that may have taken place outside of the typical tracing process. The data has not been collected for official statistics purposes which means it has not undergone the same level of quality assurance as official statistics and will be subject to future revisions. We are publishing this to provide a weekly summary of contact tracing activity in Wales during the coronavirus (COVID-19) pandemic.

Due to an increase in the number of positive cases and contacts eligible for follow up by local contact tracing teams, from the week commencing 6 September 2021 Welsh Government introduced a national framework to prioritise cases that have a higher risk of onward transmission or that involve vulnerable individuals. This means that the positive cases reached are likely to be those classed as the highest priority from a public health protection perspective.

Main results

In the latest week (5 to 11 September 2021):

  • of the 16,969 positive cases that were eligible for follow-up, 13,602 (80.2%) were reached and asked to provide details of their recent contacts
  • of the 30,258 close contacts that were eligible for follow-up, 22,935 (75.8%) were successfully contacted and advised accordingly, or had their case otherwise resolved
  • the total number of positive cases and close contacts eligible for follow up in a single week was the highest since records began.

In total, since 21 June 2020:

  • of the 271,343 positive cases that were eligible for follow-up, 264,380 (97.4%) were reached and asked to provide details of their recent contacts
  • of the 599,676 close contacts that were eligible for follow-up, 556,524 (92.8%) were successfully contacted and advised accordingly, or had their case otherwise resolved
Table 1: Positive cases referred to the contact tracing system, up to 11 September 2021
  Latest week 5 to 11 September 2021 Cumulative total 21 June 2020 to 11 September 2021
Eligible for follow-up by local contract tracing teams 16,969 271,343
Not eligible for follow-up by local contact tracing teams 1,146 48,526
Total 18,115 319,869

Source: Digital Health and Care Wales (DHCW)

Information on the types of cases not eligible for follow-up by local contact tracing teams is provided in the quality and methodology information section.

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The chart shows that, over the latest week, 80.2% of those eligible for follow-up were reached and 19.8% were not reached.
Table 2: People identified as close contacts, up to 11 September 2021
  Latest week 5 to 11 September 2021 Cumulative total 21 June 2020 to 11 September 2021
Eligible for follow-up by local contract tracing teams 30,258 599,676
Not eligible for follow-up by local contact tracing teams 2246 74,470
Total 32,504 674,146

Source: Digital Health and Care Wales (DHCW)

These figures relate to all close contacts identified in the reporting period shown. Some may have been identified by positive cases referred to the contact tracing system prior to the reporting period. The figures may also include some close contacts eligible for follow-up by local contact tracing teams that were identified by positive cases escalated to regional teams for onward management.

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The chart shows that, over the latest week, 75.8% of close contacts eligible for follow-up were successfully contacted and advised and 24.2% were not.
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From December 2020 the rolling average generally decreased, reaching a similar level to early September 2020. From early June 2021 this has been increasing, with a local peak in mid-July 2021 which was surpassed in August 2021.

Number of positive cases and close contacts eligible for follow-up by local contact tracing teams on StatsWales

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From December 2020 the rolling average generally decreased, reaching a similar level to early September 2020. From early June 2021 this has been increasing, with a local peak in mid-July 2021 which was surpassed in August 2021.

Number of positive cases and close contacts eligible for follow-up by local contact tracing teams on StatsWales

Charts 3 and 4 represent the daily number of positive cases and close contacts eligible for follow up. The number of cases eligible for follow-up for recent weeks may change slightly compared to previous releases due to cases being flagged as not eligible following further investigation by contact tracing teams. More details on this process can be found in the quality and methodology information section.

Variation between days reflects difference in demand on the system (for example, number of tests performed) with some days seeing more cases feeding through to contact tracing teams. A peak in positive cases or close contacts can occur as a result of:

  • a backlog of cases from previous days
  • a large batch of test results being submitted
  • a new testing site opening
  • more testing capacity becoming available

The total number of positive cases and close contacts eligible for follow up in a single week was the highest in the week 5 to 11 September 2021 where there were 16,969 positive cases and 30,258 close contacts eligible for follow up by local contact tracing teams.

Time taken to reach positive cases and close contacts

In the latest week (5 to 11 September 2021)

Positive cases

  • Of the 16,969 positive cases that were eligible for follow-up, 40.6% were reached within 24 hours of referral to the contact tracing system. This equates to 50.7% of those successfully reached being reached within 24 hours.
  • 59.1% of positive cases that were eligible for follow-up were reached within 48 hours. This equates to 73.7% of those successfully reached being reached within 48 hours.

Close contacts

  • Of the 30,258 close contacts that were eligible for follow-up, 52.0% were reached within 24 hours of being identified by a positive case. This equates to 68.6% of those successfully reached being reached within 24 hours.
  • 65.3% of close contacts that were eligible for follow-up were reached within 48 hours of being identified by a positive case. This equates to 86.2% of those successfully reached being reached within 48 hours.
  • From the time positive cases were referred to the contact tracing system, 14.9% of all close contacts that were eligible for follow-up were reached within 24 hours. This equates to 19.8% of those successfully reached being reached within 24 hours.
  • From the time positive cases were referred to the contact tracing system, 36.2% of all close contacts that were eligible for follow-up were reached within 48 hours. This equates to 48.0% of those successfully reached being reached within 48 hours.

In recent weeks the time taken to reach positive cases and the time taken to reach close contacts from the time positive cases were referred to the contact tracing system have seen a decrease in the percentage reached within 24 and 48 hours. This is likely due to a larger number of positive cases and close contacts eligible for follow up by local contact tracing teams. The number of positive cases and close contacts eligible for follow up are similar to those seen at the peak in December 2020.

Data for 1 to 21 June 2020

Early reporting, covering the first three weeks of contact tracing in Wales, was based on data reported by local and regional contact tracing teams prior to the introduction of the national digital system.

In Wales, during the period from 1 to 21 June 2020, 1,905 positive cases were referred to local and regional contact tracing teams. This resulted in 2,616 contacts identified for follow-up, of which 2,117 were successfully contacted and advised accordingly.

There will be a small amount of overlap in the reporting from the national digital system and the early reporting provided by local and regional contact tracing teams. For this reason we would not recommend combining figures from the two different reporting streams. Cumulative reporting in this and future versions of this release will focus on data from 21 June 2020.

Quality and methodology information

Data source

This data is management information provided to the Welsh Government by Digital Health and Care Wales. We are publishing this to provide a weekly summary of contact tracing activity in Wales during the coronavirus (COVID-19) pandemic. This data has not undergone the same level of quality assurance as official statistics and the data may be subject to future revisions.

Data included in this release was extracted from the contact tracing system at 11:09 on 14 September 2021. This extract was taken 3 days after the end of the reporting period in order to capture follow-up activity relating to cases referred towards the end of the reporting period.

Positive cases and close contacts not eligible for follow-up

The majority of cases not eligible for follow-up by local contact tracers occur in closed settings such as hospitals, care homes and prisons. These cases are escalated to regional teams for onward management.

Positive cases and close contacts that are resident outside of Wales are also not eligible for follow-up by local contact tracing teams. Public Health Wales refer these cases to the relevant public health agency for onward tracing. These cases would have been included in the numbers eligible for follow-up in statistical releases prior to the 10 September 2020.

For cases in halls of residence, students may have been contacted by text or by their university to advise them to isolate and not by the local contact tracing team. This type of activity is not captured in the contact tracing data. Also, school “bubble” contacts aren’t subject to formal contact tracing process as they are contacted directly by their school and provided the necessary public health and isolation guidance. For this reason, we have excluded these contacts from the close contacts statistics presented in this release.

Time taken to reach positive cases and close contacts

For positive cases, the time taken to reach them measures the time between the case being referred to the contact tracing system and them being successfully contacted. For close contacts there are two measures. The first looks at the time between the close contact being identified by a positive case and them being successfully contacted. The second looks at the difference between the positive cases that identified them being referred to the contact tracing system and when the close contact was successfully contacted. The latter measure for close contacts excludes a small number that could not be linked back to the positive case that identified them.

The date and time that a positive case or close contact was successfully contacted is taken to be the earliest of a number of events captured in the system. These include:

  • successful phone call record (including initial phone call from contact tracers to invite cases and contacts to complete the e-form)
  • completion of the contact interview
  • first daily check-up
  • close contacts or other exposures being entered into the contact tracing system (for positive cases only)
  • case marked as ‘resolved’

These events have been chosen as they all indicate that a contact tracer has successfully been in touch with the individual. The range of events is necessary because phone call records do not exist for all positive cases and close contacts. This may arise, for example, where multiple cases live in the same household and the information is captured through a single phone call, rather than one for each individual.

When close contacts are identified by a positive case outside of Wales or through the NHS app, these are inputted into the system manually as the positive case that identified them does not exist in the Welsh contact tracing system. As the positive case is not in the Welsh contact tracing system, these close contacts should not be included in the timeliness measure from the time positive cases are referred to the contact tracing system. We were recently made aware of the processes around these close contacts and from the week commencing 16 May 2021, we have removed these close contacts from this measure and the historical data to more accurately reflect the contact tracing system. As these close contacts are eligible for follow up within the Welsh contact tracing system, they still appear in all other figures relating to close contacts presented in this release.

The percentage of close contacts reached within 24 hours and 48 hours from the time positive cases were referred to the contact tracing system will appear higher than previous publications as a result of this change. Since September 2020 when the process for these close contacts was implemented, there have been an average of 60 close contacts per week identified by a positive case outside of Wales or through the NHS app. For the week 16 to 22 May 2021 when this change in methodology was first implemented, the change resulted in an increase of 6 percentage points in the timeliness measure within 24 hours and 7 percentage points in the timeliness measure within 48 hours from the time positive cases were referred to the contact tracing system.

School bubble data

School 'bubble' contacts aren’t subject to formal contact tracing process, as they are contacted directly by their school and provided the necessary public health and isolation guidance. For this reason, from the release published 25 March 2021 we have excluded these contacts from the close contacts statistics presented in this release. All historical data has been updated to reflect this change.

Positive cases will most likely have close contacts outside of their bubble which have been generated in school which will be communicated to local contact tracing teams and will be eligible for follow up, these contacts remain in the statistics presented in this release

Data presented in this release is broadly comparable with publications prior to the 25 March 2021, though we advise against using the publications on 11 February and 18 February 2021 to make comparisons, where the issues in the school 'bubble' data have had the most effect, and the publication on 23 March 2021 where all school contacts were removed while we investigated a data quality issue. Comparisons can be made within the time series data in this release where school 'bubble' data has been removed throughout.

Information and guidance on how schools and settings can continue to make their sites as safe as possible for staff and learners, including school 'bubbles' is outlined in the Operational guidance for schools and settings

Further quality and methodology information

Close contacts ‘otherwise resolved’ covers a small number of instances where the same contact is identified by multiple positive cases concurrently. On these occasions, contact tracing teams will work from a single record relating to that contact and mark the additional records as resolved.

The number of cases referred for contact tracing is different to the number of new cases published by Public Health Wales. These sources of data are not directly comparable due to differences in timing and the level of validation carried out, as cases submitted to the contact tracing system need to be handled manually by contact tracing teams.

Contacts generated from positive cases outside of Wales which are eligible for follow up by local contact tracing teams in Wales are included as close contacts in these statistics. These contacts may have an effect on the timeliness measures from index case creation and we are conducting further investigation with Digital Health and Care Wales (DHCW) colleague into these specific scenarios.

On 17 December 2020, the NHS Wales Test Trace Protect (TTP) service rolled out a new function aimed at giving people the ability to provide details of their close contacts via a new e-form. Cases receive an initial phone call from contact tracers to invite them to complete the e-form and this call is defined as a successful contact. This information is included in the data shown in this release and will have an impact on the overall percentage of both positive cases and contacts successfully contacted, and the percentage of positive cases and contacts reached within 24 and 48 hours. Due to the reduction in positive cases in Wales and therefore, lower numbers of cases and contacts currently requiring contact tracing, most local contact tracing teams are prioritising phone calls over the use of the e-form. This means that e-forms will account for extremely small numbers within the data presented in this publication. We continue to work with colleagues to monitor use of the e-form within the contact tracing system and will include further information on this if use of the e-form begins to increase considerably.

For the week 21 to 27 March 2021, there was a large increase in the number of contacts eligible for follow up in Swansea Bay University Health Board which can be seen in the associated tables published alongside this release. We believe this to be a result of some school contacts being uploaded incorrectly for this region. This increase had a small impact on the national figures presented in this release for the percentage of contacts reached but a larger impact on time taken to reach close contacts. Regions have been reminded of the guidance on uploading school “bubbles” into the system to avoid further issues with the data.

From the 4 March 2021 publication, data for travellers arriving from outside the UK’s Common Travel Area is no longer included in the figures presented in this release and has been removed retrospectively from historic data. Compared to the data as it was published on 25 February 2021, this resulted in a small reduction in the number of index cases and close contacts in the data published on 4 March 2021 as these arriving international travellers represented less than 3% of the weekly cases. These citizens are isolating due to their travel and to avoid any potential transmission of variants of concern. As such they are subject to a separate managed quarantine process. If an arriving international traveller subsequently tests positive, they will then become an index case and therefore be subject to the full contact tracing process and appear in the statistics presented.

In the 17 May 2021 release, Digital Health and Care Wales (DHCW) changed the contact tracing data to remove duplicate records. This change was applied to historical data from the start of this dataset (21 June 2020) onwards. Duplicate records occur where more than one positive case identifies the same close contact. Following this change, close contacts are now only counted once in the figures eligible for follow up. Previously they were counted each time they were identified by a positive case. Duplicate records account for up to 5% of the eligible close contacts in each week.

In recent weeks, all measures for the time taken to reach positive cases and close contacts have seen a decrease. This is likely due to a larger number of positive cases and close contacts eligible for follow up by local contact tracing teams.

As of 7 August 2021, adults who have been fully vaccinated and received the vaccine in the UK and those under the age of 18 will no longer have to self-isolate if they are identified as close contacts of someone who has tested positive for COVID-19. Close contacts are still contacted by the contact tracing team and are therefore still included in the statistics presented in this publication. We are working with colleagues in DHCW to determine data quality and possible further breakdowns of the data.

Data for contact tracing via the NHS COVID-19 App is published by The Department of Health and Social Care and includes data on users who have completed the symptom checker, test results received, users notified to self-isolate and check in events that have taken place. Latest published data and more information on this can be found at: What data is available about how the NHS COVID-19 app is being used?

National Statistics status

These statistics are not National Statistics. However, as far as has been practicable, they have been collected and validated in accordance with the pillars and principles within the Code of Practice for Statistics. We continue to develop the data collection and quality assurance process to improve the data.

These statistics have been produced quickly in response to developing world events.

Well-being of Future Generations Act

The Well-being of Future Generations Act 2015 is about improving the social, economic, environmental and cultural wellbeing of Wales. The Act puts in place seven wellbeing goals for Wales. These are for a more equal, prosperous, resilient, healthier and globally responsible Wales, with cohesive communities and a vibrant culture and thriving Welsh language. Under section (10)(1) of the Act, the Welsh Ministers must (a) publish indicators ('national indicators') that must be applied for the purpose of measuring progress towards the achievement of the wellbeing goals, and (b) lay a copy of the national indicators before Senedd Cymru. The 46 national indicators were laid in March 2016.

Information on the indicators, along with narratives for each of the well-being goals and associated technical information is available in the Well-being of Wales report.

Further information on the Well-being of Future Generations (Wales) Act 2015.

The statistics included in this release could also provide supporting narrative to the national indicators and be used by public services boards in relation to their local wellbeing assessments and local wellbeing plans.

Further information

For information and advice on contact tracing please refer to our Test, trace, protect: coronavirus guidance page.

Next update

This is currently a weekly statistical release. It will be published at 09:30am every Thursday. We will review the frequency in line with changing user need.

The next release will be on Thursday 23 September 2021.

We are considering reducing the frequency of some of the COVID-19 related statistical releases, including this publication. We welcome any comments or feedback on how you use these releases, and any changes to them via kas.covid19@gov.wales.

Contact details

Statistician: Alex Fitzpatrick (for queries about the data)
Telephone: 0300 025 9016
Email: kas.covid19@gov.wales

Media: 0300 025 8099

SFR 286/2021

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