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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.

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.

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.

For the latest week (21 to 27 March) there has been 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 increase has 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. We are working closely with local contact tracing teams and NHS Wales Informatics Service (NWIS) to further understand this increase.

Main results

In the latest week (21 to 27 March 2021):

  • of the 1,183 positive cases that were eligible for follow-up, 1,167 (99%) were reached and asked to provide details of their recent contacts
  • of the 4,323 close contacts that were eligible for follow-up, 4,154 (96%) were successfully contacted and advised accordingly, or had their case otherwise resolved

In total, since 21 June 2020:

  • of the 172,982 positive cases that were eligible for follow-up, 172,362 (99.6%) were reached and asked to provide details of their recent contacts
  • of the 396,332 close contacts that were eligible for follow-up, 374,233 (94%) were successfully contacted and advised accordingly, or had their case otherwise resolved
Table 1: Positive cases referred to the contact tracing system, up to 27 March 2021
  Latest week 21 to 27 March 2021 Cumulative total 21 June 2020 to 27 March 2021
Eligible for follow-up by local contract tracing teams 1,183 172,982
Not eligible for follow-up by local contact tracing teams 269 31,951
Total 1,452 204,933

Source: NHS Wales Informatics Service (NWIS)

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, 99% of those eligible for follow-up were reached and 1% were not reached. In total, since 21 June, 100% were reached and 0% were not reached.

Positive cases eligible for follow-up by local contact tracing teams, up to 27 March 2021 (MS Excel)

Table 2: People identified as close contacts, up to 27 March 2021
  Latest week 21 to 27 March 2021 Cumulative total 21 June 2020 to 27 March 2021
Eligible for follow-up by local contract tracing teams 4,323 396,332
Not eligible for follow-up by local contact tracing teams 373 13,099
Total 4,696 409,431

Source: NHS Wales Informatics Service (NWIS)

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, 96% of close contacts eligible for follow-up were successfully contacted and advised and 4% were not. In total, since 21 June, 94% were successfully contacted and advised and 6% were not.

Close contacts eligible for follow-up by local contact tracing teams, up to 27 March 2021 (MS Excel)

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Chart 3 shows the daily number of positive cases eligible for follow up since 21 June 2020. The 7-day rolling average increased from late August 2020 to the start of November 2020 but subsequently dropped to lower levels. However, there was a steep increase in the rolling average from the end of November 2020 until a peak was reached in mid December 2020. Since then, the rolling average has generally been falling and is now at a similar level to mid September 2020.

Daily positive cases eligible for follow-up by local contact tracing teams, up to 27 March 2021 (MS Excel)

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Chart 4 shows the daily number of close contacts eligible for follow-up since 21 June 2020. There has been an overall upward trend in the 7-day rolling average since late August 2020 up to a peak in late December 2020, despite some decreases during that time. Since then the rolling average has generally been falling, and is now at a similar level to mid September 2020.

Daily close contacts eligible for follow-up by local contact tracing teams, up to 27 March 2021 (MS Excel)

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 (e.g. 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 or more testing capacity becoming available.

Time taken to reach positive cases and close contacts

In the latest week (21 to 27 March 2021)

Positive cases

  • Of the 1,183 positive cases that were eligible for follow-up, 94% were reached within 24 hours of referral to the contact tracing system. This equates to 95% of those successfully reached being reached within 24 hours.
  • 97% of positive cases that were eligible for follow-up were reached within 48 hours. This equates to 99% of those successfully reached being reached within 48 hours.

Close contacts

  • Of the 4,323 close contacts that were eligible for follow-up, 88% were reached within 24 hours of being identified by a positive case. This equates to 92% of those successfully reached being reached within 24 hours.
  • 92% of close contacts that were eligible for follow-up were reached within 48 hours of being identified by a positive case. This equates to 96% of those successfully reached being reached within 48 hours.
  • From the time positive cases were referred to the contact tracing system, 54% of all close contacts that were eligible for follow-up were reached within 24 hours. This equates to 56% of those successfully reached being reached within 24 hours.
  • From the time positive cases were referred to the contact tracing system, 79% of all close contacts that were eligible for follow-up were reached within 48 hours. This equates to 82% of those successfully reached being reached within 48 hours.

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 the NHS Wales Informatics Service. 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 11:30 on 30 March 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.

Data included in this release was extracted from the contact tracing system at 12:50 on 16 March 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.

Time taken to reach positive cases and close contacts

Following the identification of a data quality issue around the uploading process of school 'bubble' contacts into the contact tracing system, we excluded all school data from the timeliness measures published in the release published Thursday 18 March. This was due to the issue impacting the measures for time taken to reach close contacts resulting in figures which we believe to be misleading. This approach also removed a small number of school contacts that would be eligible for follow up from the timeliness measures.

Following further data quality checks and discussions with local contact tracing teams, school “bubble” data has been excluded from the close contacts statistics presented since the 25 March 2021 release and historical data has been updated to reflect this change. We have made this change to ensure transparency and more clearly reflect the performance of the contact tracing system in Wales.

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. 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 publication though we advise against direct comparisons with weeks beginning 31 January and 7 February 2021 where the issues in the school 'bubble' data have had the most effect and the week beginning 7 March 2021 where all school contacts were removed while we investigated a data quality issue.

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

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.

  • 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.

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.

For the latest week (21 to 27 March 2021) there has been 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 increase has 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. We are working closely with local contact tracing teams and NHS Wales Informatics Service (NWIS) to further understand this increase.

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 has 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.

On 17 December, 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 very 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.

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 well-being assessments and local wellbeing plans.

Next update

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

The next release will be on Thursday 8 April 2021.

We want your feedback

We welcome any feedback on any aspect of these statistics which can be provided by email to 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 97/2021

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