The Department of Health today published the next in the series of weekly results from its COVID-19 Infection Survey (CIS). The findings set out in this report relate to modelled positivity estimates for NI for the week up to the 26th February 2022. 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 residential households).
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 (20 February – 26 February 2022), it is estimated that 106,300 people in Northern Ireland had COVID-19 (95% credible interval: 90,700 to 123,700).
- this equates to 5.79% of the population (95% credible interval: 4.95% to 6.74%) or around 1 in 17 people (95% credible interval: 1 in 20 to 1 in 15).
- modelling suggests the percentage of people testing positive decreased in the week ending 26 February in Northern Ireland.
- in the latest six-week period, there were 16,934 swab tests taken in total from 11,988 participants. Of these, 965 participants tested positive from 702 different households.
- in the latest two-week period, of the 5,304 participants in the study, 289 tested positive from 223 households.
- the percentage of people testing positive in Northern Ireland has decreased amongst children and young adults and there are possible early signs of an increase in those aged 70 and over in the most recent week.
- the percentage of infections compatible with the Omicron BA.2 variant increased in England, Wales, and Scotland and decreased in Northern Ireland in the week ending the 26 February 2022; the percentage of cases compatible with the Omicron BA.1 variant decreased in England, Wales, and Northern Ireland and increased in Scotland over the same period.
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.1.1, BA.2 and BA.3)
The Omicron variant BA.1 has changes in one of the three genes that the coronavirus swab used in the survey tests detects, known as the S-gene. This means 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), not detecting the S-gene in combination with detecting the other two genes (ORF1ab and N-genes) is a reliable indicator of this Omicron BA.1 variant. However, as the viral load decreases (for example, if someone is near the end of their recovery from the infection), not detecting the S-gene is a less reliable indicator of this Omicron variant. The sub-variant Omicron BA.1.1 also mostly has gene pattern ORF1ab + N. Therefore, gene pattern matching used in the main variant analysis cannot distinguish between Omicron BA.1 and Omicron BA.1.1.
The Omicron variant BA.2 does not have changes in the S gene, and therefore all three genes, or the S-gene and either ORF1ab or N, will usually be detected in infections with this variant. Delta also does not have changes in the S-gene, and therefore the same sets of genes will usually be detected with Delta and Omicron BA.2. However, the genome sequencing analysis shows that a clear majority of cases where the S-gene is detected are now Omicron BA.2, with relatively few being Delta. For this reason, we now label cases with gene patterns ORF1ab + N + S, ORF1ab + S and N + S as “compatible with the Omicron BA.2 variant” in our main variant analysis. This is because estimates are now likely to mostly reflect trends in BA.2, although Delta may still be having a very small impact.
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:
- 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.
- 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.
- 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 communal establishments.
- 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.
- 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.
- Further information about quality and methodology associated with the survey can be found on the ONS website.
- This publication is available on the Department of Health website.
- Additional information is available from:
Information Analysis Directorate
Department of Health
Annex 2, Castle Buildings
Stormont
Belfast BT4 3SQ
Telephone: 028 9052 2340 E-mail: statistics@health-ni.gov.uk