Coronavirus (Covid-19) Infection Survey Northern Ireland – 20 - 26 February 2021

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 Northern Ireland for the week up to the 26 February 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 (20 February – 26 February), it is estimated that 5,700 people in Northern Ireland had COVID-19 (95% credible interval: 3,300 to 8,900). 
• This equates to 0.31% of the population (95% credible interval: 0.18% to 0.48%) or around 1 in 325 people (95% credible interval 1 in 560 to 1 in 205).
• This is based on statistical modelling of the trend in rates of positive nose and throat swab results. Modelling suggests that in the most recent week, the percentage of people testing positive in Northern Ireland has continued to decrease.
• In the latest six-week period, there were 23,199 swab tests taken in total from 11,302 participants. Of these, 197 participants tested positive from 175 different households.
• In the latest two-week period, of the 5,636 participants in the study, 28 tested positive from 23 households.
• Rates appear to have decreased across all ages in recent weeks.

New variant analysis:

A new variant of the coronavirus (COVID-19) was identified in the UK in mid-November 2020. The new UK variant of COVID-19 has changes in one of the three genes which coronavirus swab tests detect, known as the S-gene. This means in cases compatible with the new variant, the S-gene is no longer detected by the current test. While there are other reasons why a positive swab test may not detect the S-gene, absence of the S-gene has become a reliable indicator of the new UK variant in COVID-19.

In contrast the South African and Brazilian variants have an S-gene that is detectable with the current test and will therefore be included in the “not compatible with new variant” group of COVID-19 where the virus level is high enough to identify this. Which of these types of COVID-19 are compatible with the South African and Brazilian variants cannot be identified from the swab PCR test alone. You can read more about the new UK variant in a recent Office for National Statistics blog(external link opens in a new window / tab).

In Northern Ireland, the percentage testing positive compatible with the new UK variant decreased in Northern Ireland in the week ending 26 February 2021.

It should be noted that there is considerable uncertainty around these estimates due to the small numbers of new variant compatible positives detected in Northern Ireland and also given that not all cases that are positive on the ORF1ab and N-genes will be the new variant.