Coronavirus (Covid-19) Infection Survey Northern Ireland – 10 December to 16 December 2021

Date published: 23 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 NI for the week up to the 16 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 (10 December – 16 December), it is estimated that 37,800 people in Northern Ireland had COVID-19 (95% credible interval: 29,100 to 47,700). 
  • This equates to 2.06% of the population (95% credible interval: 1.59% to 2.60%) or around 1 in 50 people (95% credible interval 1 in 65 to 1 in 40).
  • Modelling suggests the trend in the percentage of people testing positive was uncertain in the week ending 16 December in Northern Ireland.
  • In the latest six-week period, there were 16,762 swab tests taken in total from 11,992 participants. Of these, 284 participants tested positive from 221 different households.
  • In the latest two-week period, of the 5,147 participants in the study, 108 tested positive from 83 households.
  • In the week ending 16 December 2021, the percentage of cases compatible with the Omicron variant (B.1.1.529) increased in all four UK countries. In the same week, the percentage of cases compatible with the Delta variant (B.1.617.2 and its genetic descendants) has decreased in England, Wales and Northern Ireland, and the trend was uncertain in Scotland (see below for more information on the variant analysis undertaken).

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 and its genetic descendants
  • Omicron: B.1.1.529 (which includes sublineages BA.1, BA.2 and BA.3)

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. In the four weeks up to 6 December 2021, results showed that over 94% of all coronavirus (COVID-19) infections, where a genetic sequence could be obtained, were genetically compatible with the Delta variant or its descendants.

The Omicron variant (B.1.1.529) of COVID-19 has changes in one of the three genes that coronavirus swab tests detect, known as the S-gene. This means in cases compatible with the Omicron variant, the S-gene is no longer detected by the current test. When there is a high viral load (for example, when a person is most infectious) absence of the S-gene in combination with the presence of the other two genes (ORF1ab and N-genes) is a reliable indicator of the Omicron variant (B.1.1.529). However, as the viral load decreases (for example, if someone is near the end of their recovery from the infection), the absence of the S-gene is a less reliable indicator of the Omicron variant.

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.
  2. 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.
  3. 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.
  4. 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.
  5. 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.
  6. Further information about quality and methodology associated with the survey can be found on the ONS website.
  7. This publication is available on the DoH website.
  8. Additional information is available from:

Information Analysis Directorate
Department of Health
Annex 2, Castle Buildings
Belfast BT4 3SQ
Telephone:          028 9052 2340         E-mail:

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