Coronavirus (Covid-19) Infection Survey Northern Ireland – 25 November to 1 December 2021

Date published: 10 December 2021

The Department of Health today published the next in the series of weekly results from its COVID-19 Infection Survey (CIS).

covid latest stats

The findings set out in this report relate to modelled positivity estimates for Northern Ireland for the week up to the 1 December 2021. The aims of the CIS are to estimate how many people have the infection and the number of new cases that occur over a given time as well as estimating how many people have developed antibodies to COVID-19.

The survey over time will help track the extent of infection and transmission of COVID-19 among people in the community population (those in private residences).

Key Findings

Due to the relatively small number of tests and positive swab results within our sample, credible intervals are wide and therefore results should be interpreted with caution.

  • During the most recent week of the study (25 November – 1 December), it is estimated that 39,300 people in Northern Ireland had COVID-19 (95% credible interval: 30,600 to 49,000). 
  • This equates to 2.14% of the population (95% credible interval: 1.67% to 2.67%) or around 1 in 45 people (95% credible interval 1 in 60 to 1 in 35).
  • Modelling suggests the percentage of people testing positive increased in Northern Ireland over the last two weeks, but the trend was uncertain in the week ending 1 December.
  • In the latest six-week period, there were 16,455 swab tests taken in total from 11,789 participants. Of these, 236 participants tested positive from 184 different households.
  • In the latest two-week period, of the 5,230 participants in the study, 107 tested positive from 88 households.

Variant analysis

The World Health Organization (WHO) have defined names for Variants of Concern. These are variants that the UK government has under surveillance. You can find out more in the SARS-CoV-2 variants of concern and variants under investigation in England briefing document (PDF, 2.51MB).

UK Variants of Concern:

  • Alpha: B.1.1.7
  • Beta: B.1.351
  • Gamma: P.1
  • Delta: B.1.617.2
  • Omicron: B.1.1.529

Infections compatible with the Delta variant have been the most common since the end of May 2021 in England, and since the end of July 2021 in all four UK countries. The most recent results show over 99% of all coronavirus (COVID-19) infections, where a genetic sequence could be obtained, were genetically compatible with the Delta variant or its descendants. Due to this high proportion with the same gene positivity pattern, a breakdown of infections by variant based on gene positivity patterns has not been included. The main variant analysis was last published on the 23 July 2021, where more details can be found.

To date, a very small number of infections consistent with the new Omicron variant (B.1.1529) have been identified among the survey participants. It is only when there are sufficient participants testing positive with infections compatible with the Omicron variant that a meaningful estimate of the number of people infected in the population can be produced. This variant and other variants detected in the sample will continue to be monitored.

Infections by variant will continue to be monitored and the charts and analysis will be introduced when considered helpful.

More information on how variants from positive tests on the survey are measured can be found in the ONS Understanding COVID-19 Variants blog and in the methodology article.

Notes to editors: 

  1. The Department of Health has been working along with the Public Health Agency, Northern Ireland Statistics and Research Agency and the Office for National Statistics (and its various survey partners) to extend the COVID-19 Infection Survey to Northern Ireland. Fieldwork in Northern Ireland began on 27 July 2020.
  1. All results are provisional and subject to revision. Due to relatively small number of tests and positive swab tests within the sample, credible intervals are wide and therefore results should be interpreted with caution.
  1. These statistics refer to infections reported in the community (i.e. private households). These figures exclude infections reported in hospitals, care homes and/or other institutional settings.
  1. Estimates of the total national proportion of the population testing positive for COVID-19 are adjusted to be representative of the population of Northern Ireland that live in private residential households in terms of age, sex and region.
  1. Weekly reports are to be published with findings from the COVID-19 Infection survey. It is anticipated that new and further analyses will be added to the weekly reports over time.
  1. Further information about quality and methodology associated with the survey can be found on the ONS website.

  1. This publication is available online.
  1. Additional information is available from:
    Information Analysis Directorate
    Department of Health
    Annex 2, Castle Buildings
    Belfast BT4 3SQ
    Telephone:  028 9052 2340         E-mail:
  2. For media enquiries please contact the DoH Press Office by email
  3. Follow us on Twitter @healthdpt.
  4. The Executive Information Service operates an out of hours service For Media Enquiries Only between 1800hrs and 0800hrs Monday to Friday and at weekends and public holidays. The duty press officer can be contacted on 028 9037 8110.

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