Coronavirus (Covid-19) Infection Survey Northern Ireland – 24 October to 30 October 2021

Date published: 5 November 2021

The findings set out in this report relate to modelled positivity estimates for Northern Ireland for the week up to the 30 October 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 (24 October – 30 October), it is estimated that 27,400 people in Northern Ireland had COVID-19 (95% credible interval: 20,000 to 37,000).
• This equates to 1.49% of the population (95% credible interval: 1.09% to 2.02%) or around 1 in 65 people (95% credible interval 1 in 90 to 1 in 50).
• Modelling suggests the percentage of people testing positive continued to increase in the week ending 30^th October in Northern Ireland.
• In the latest six-week period, there were 15,654 swab tests taken in total from 11,583 participants. Of these, 152 participants tested positive from 117 different households.
• In the latest two-week period, of the 4,606 participants in the study, 64 tested positive from 50 households.

Variant analysis

The Alpha variant (B.1.1.7) of COVID-19, identified in the UK in mid-November 2020, has changes in one of the three genes that COVID-19 swab tests detect, known as the S-gene. This means in cases compatible with the Alpha variant, the S-gene is not detected by the current test and has the pattern ORF1ab+N (S gene negative) in the main variant analysis. Other variants – including both Delta (B.1.617.2) and Beta (B.1.351) – are positive on all three genes, with the pattern ORF1ab+S+N. Almost all ORF1ab+S+N cases in the UK will now be the Delta variant, so this group is labelled “Compatible with the Delta variant”.

More information on individual variants and where they were first detected is available on the government variant dashboard.

Since the end of July 2021, infections compatible with the Delta variant have been the most common 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 the Delta variant or a genetic descendant/sub-lineage of the Delta variant. These all have the same gene positivity pattern. 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. Infections by variant will continue to be monitored and the charts and analysis will be introduced when considered helpful.

ONS has published a blog where more can be read about COVID-19 variants.