Coronavirus (Covid-19) Infection Survey, Northern Ireland: weekly report

Date published: 13 January 2023

The findings set out in this report relate to modelled positivity estimates for NI for the week up to the 31 December 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 (25 December – 31 December 2022), it is estimated that 129,100 people in Northern Ireland had COVID-19 (95% credible interval: 109,800 to 151,200).
• this equates to 7.04% of the population (95% credible interval: 5.99% to 8.24%) or around 1 in 14 people (95% credible interval: 1 in 17 to 1 in 12).
• modelling suggests the trend in the percentage of people testing positive increased in the two weeks up to 31 December 2022 in Northern Ireland but the trend was uncertain in the most recent week.
• the percentage of people testing positive for COVID-19 generally increased in children in recent weeks, however the trend was uncertain over the most recent week. The percentage of people testing positive for COVID-19 increased in young adults and the older ages in recent weeks.

Variant analysis

Currently, the variants under surveillance in the UK are:

• omicron, including sub-lineages BA.2, BA.4 and BA.5, and their sub-lineages.

The cycle threshold (Ct) value reflects the quantity of virus (also known as viral load) found in a swab test. A lower Ct value indicates a higher viral load. The latest Ct values of coronavirus (COVID-19) positive tests, as well as analysis of the genetic lineages of COVID-19 seen in the samples that are sequenced, are provided in the Coronavirus (COVID-19) Infection Survey: technical dataset.

Since the end of June 2022, most COVID-19 infections in the UK have been Omicron variant BA.5 or its sub-lineages. One of these BA.5 sub-lineages, BQ.1, has been increasing in recent months. In the week ending 25 December 2022, BQ.1 comprised 55.1%, and other BA.5 variants (and sub-lineages, excluding BQ.1) comprised 9.7% of all sequenced COVID-19 infections. The variant BA.2.75 and its sub-lineages (that include XBB and its sub-lineages, and CH.1.1 and its sub-lineages) comprised 33.6%, with the sub-lineage CH.1.1 and its sub-lineages comprising 19.1%, and the sub-lineage XBB and its sub-lineages comprising 7.1% of sequenced infections in the week ending 25 December 2022. In the same week, BA.4 and its sub-lineages comprised 0.6% of sequenced infections.

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 the Coronavirus (COVID-19) Infection Survey methods article.

The last published main variant analysis was included in COVID-19 Infection Survey, Northern Ireland: Weekly Report 8 July 2022. This showed a very high proportion of infections compatible with the BA.4 and BA.5 variants, so a breakdown of infections by variants is not included in this release. Infections by variant will continued to be monitored and analysis will be reintroduced when considered helpful.