Whole genome sequencing

As part of the COVID-19 pandemic response, the Public Health Agency Health Protection Surveillance team established a new surveillance system to monitor SARS-CoV-2 genomic variants.

The Surveillance team used reflex assay (genotyping) to screen for variants of concern, and used whole genome sequencing results to monitor the prevalence of genomic lineages, which provided a more detailed view of the genome. The team also used transmission chain analysis to provide predictions on potential transmission events, in order to identify the source of infection and help reduce the chance of more transmission.

During the COVID-19 pandemic, variants in Northern Ireland were identified using genomic surveillance. This information was used to advise public health action in controlling the spread of COVID-19. Screening for variants continues to be important for making informed public health decisions, particularly if we identify a variant shown to cause more severe illness, or if vaccines might not offer as much protection against a new variant.

The latest SARS-CoV-2 genomic variants data for Northern Ireland are presented in the weekly COVID-19 bulletin, which can be accessed here: COVID-19 Epidemiological Bulletin | HSC Public Health Agency (hscni.net)

Further information about SARS-CoV-2 variants can be found in UKHSA’s reports here:

Investigation of SARS-CoV-2 variants: technical briefings - GOV.UK (www.gov.uk) and

SARS-CoV-2: genome sequence prevalence and growth rate - GOV.UK (www.gov.uk)

COVID-19 Genomics Bulletin

This report describes the epidemiology of SARS-CoV-2 (the virus that causes COVID-19) variants in Northern Ireland.

The availability of SARS-CoV-2 sequencing results is affected the current COVID-19 testing policy and practice. We continue to monitor the circulating lineages detected through clinical testing and community sentinel surveillance for changes in prevalence of genomic variants and emergence of novel variants. We use intelligence from UKHSA and other public health authorities to monitor prevalence of mutations that may be associated with changes in immunity or severity.

It should be noted that date ranges in this report are different from those reported in the COVID-19 Epidemiological Bulletin, available here.

Grouping of lineages into their parent lineages is subject to change, as variant definitions and lineages under monitoring are revised.


 

1 Summary

  • In the 8 epidemiological weeks (15 April 2024 to 09 June 2024), 192 COVID-19 samples were sequenced in Northern Ireland.

  • The current most common SARS-CoV-2 variant in Northern Ireland is KP (V-23DEC-01), with 9 sequenced samples, or 50% of all sequenced samples (100% of those with a lineage assigned) in the week commencing 03 June 2024.

  • More information about prevalence and growth rates of SARS-CoV-2 lineages circulating in the UK can be found in UKHSA reports published here.


 

2 Current Variant View - last 8 weeks

This section summarises the SARS-CoV-2 sequencing data for Northern Ireland for the last 8 weeks of sequencing data available (15 April 2024 to 09 June 2024).

In the last 8 weeks of sequencing data, the following parent lineages have been detected: KP, JN.1, BA.3, and BA.2. The number of sequenced samples can be seen in Table 2.1 and Figure 2.1, and the numbers as a percentage of total sequenced samples are shown in Figure 2.2. The age group distribution by parent lineage is shown in Figure 2.3.

Please note that numbers of sequenced samples per week may change retrospectively due to the delay in sequencing.

Recombinant refers to any lineage starting with “X” that does not fall under any other parent lineage definition.


 

Table 2.1. Number (Percentage) of sequenced samples for variants in Northern Ireland over the last 8 epidemiological weeks (week commencing)

Variant (parent lineage)

2024-04-15

2024-04-22

2024-04-29

2024-05-06

2024-05-13

2024-05-20

2024-05-27

2024-06-03

Unassigned (Unassigned)

5 (31.2%)

5 (38.5%)

10 (43.5%)

8 (28.6%)

17 (48.6%)

13 (39.4%)

12 (46.2%)

9 (50%)

V-23DEC-01 (JN.1)

6 (37.5%)

8 (61.5%)

5 (21.7%)

4 (14.3%)

9 (25.7%)

8 (24.2%)

2 (7.7%)

1 (5.6%)

V-23DEC-01 (KP)

5 (31.2%)

0 (0)

7 (30.4%)

15 (53.6%)

8 (22.9%)

12 (36.4%)

10 (38.5%)

8 (44.4%)

VOC-22JAN-01 (BA.2)

0 (0)

0 (0)

1 (4.3%)

0 (0)

0 (0)

0 (0)

0 (0)

0 (0)

VOC-21NOV-01 (BA.3)

0 (0)

0 (0)

0 (0)

1 (3.6%)

1 (2.9%)

0 (0)

2 (7.7%)

0 (0)

Week Total

16

13

23

28

35

33

26

18


 

Sequenced COVID-19 cases in Northern Ireland, by parent lineage and day, for the last 8 weeks of sequencing data

Figure 2.1: Sequenced COVID-19 cases in Northern Ireland, by parent lineage and day, for the last 8 weeks of sequencing data


 

Percentage of sequenced COVID-19 cases in Northern Ireland, by variant and epidemiological week, for the last 8 weeks of sequencing data

Figure 2.2: Percentage of sequenced COVID-19 cases in Northern Ireland, by variant and epidemiological week, for the last 8 weeks of sequencing data


 


 

Total number of sequenced COVID-19 samples in Northern Ireland by age group, faceted by parent lineage over the last 8 weeks of sequencing data

Figure 2.3: Total number of sequenced COVID-19 samples in Northern Ireland by age group, faceted by parent lineage over the last 8 weeks of sequencing data

This chart only shows counts for lineages with at least 5 sequenced samples in a given age group.

Age band information is not available for all sequences, so age band distributions should be interpreted with caution.


 

3 Variant View - last 12 months

This section summarises the COVID-19 sequencing data for Northern Ireland over the past 12 months (05 June 2023 to 09 June 2024).

The number of sequenced samples over the past 12 months can be seen in Figure 3.1 and supplementary Table 6.2, and the numbers as a percentage of total sequenced samples are shown in Figure 3.2. The age-sex distribution by parent lineages is shown in Figure 3.3.


 

Sequenced COVID-19 cases in Northern Ireland, by variant and epidemiological week for the last 12 months

Figure 3.1: Sequenced COVID-19 cases in Northern Ireland, by variant and epidemiological week for the last 12 months


 

Percentage of sequenced COVID-19 samples in Northern Ireland by epidemiological week for the last 12 months

Figure 3.2: Percentage of sequenced COVID-19 samples in Northern Ireland by epidemiological week for the last 12 months


 

Total number of sequenced COVID-19 samples in Northern Ireland by age group and sex, by parent lineage over the last 12 months

Figure 3.3: Total number of sequenced COVID-19 samples in Northern Ireland by age group and sex, by parent lineage over the last 12 months

This chart only shows counts for lineages with at least 5 sequenced samples in a given age group.


 

4 Percentage of Specimens Sequenced

Not all PCR samples are sequenced; sequencing can only be carried out on samples that have a sufficiently high viral load, which is largely determined by when the sample is taken during the course of the infection. Other factors affecting how many samples are sequenced include volume of sample available, sample quality, and sequencing laboratory capacity.

The number of COVID-19 positive PCR samples (sequenced and not sequenced) in Northern Ireland over the past 12 months (29 May 2023 to 03 June 2024) is shown in Figure 4.1. The percentage of COVID-19 positive PCR samples that have been sequenced in on a weekly basis over the past 12 months is shown in Figure 4.2, with 6.38% sequenced (4 week rolling average of 13.68%) in the week commencing 03 June 2024.

Count of sequenced and not sequenced positive COVID-19 PCR samples in Northern Ireland over the last 12 months

Figure 4.1: Count of sequenced and not sequenced positive COVID-19 PCR samples in Northern Ireland over the last 12 months


 

Percentage of positive COVID-19 samples sequenced in Northern Ireland over the last 12 months

Figure 4.2: Percentage of positive COVID-19 samples sequenced in Northern Ireland over the last 12 months


 

5 Key Definitions and Interpretation

5.1 Definitions

  • Variant nomenclature - UKHSA made changes to the variant classification system from the 1st April 2022, resulting in previously assigned Variants Under Investigation (VUIs) or Variants of Concern (VOCs) to be assigned with the V nomenclature. Details of the change to the classification system can be found in Technical briefing 39 here.

  • Lineage assignment algorithm - on 29th November 2022, the lineage assignment algorithm was switched from PangoLEARN to UShER for lineage counts. PangoLEARN uses a machine learning algorithm, whereas UShER uses phylogenetic placement and produces few unassigned lineages.

5.2 Interpretation of variant data

  • Lineage counts for recent weeks may increase due to the time lag associated with whole genome sequencing.

  • Lineage calls are subject to change following analysis of genomic sequence results, which may result in fluctuations in lineage/variant counts.

6 Appendix

6.1 Total counts by lineage for the last 8 weeks of sequencing data (15 April 2024 to 09 June 2024)

Table 6.1. Summary of variants sequenced in Northern Ireland over the past 8 weeks

Lineage

Parent Lineage

Variant

Sequenced count

BA.2

BA.2

VOC-22JAN-01

1

BA.3

BA.3

VOC-21NOV-01

4

JN.1

JN.1

V-23DEC-01

1

JN.1.1

JN.1

V-23DEC-01

1

JN.1.16

JN.1

V-23DEC-01

6

JN.1.16.1

JN.1

V-23DEC-01

10

JN.1.18

JN.1

V-23DEC-01

5

JN.1.4.5

JN.1

V-23DEC-01

2

JN.1.48.1

JN.1

V-23DEC-01

4

JN.1.7

JN.1

V-23DEC-01

3

JN.1.8.1

JN.1

V-23DEC-01

2

JN.1.9.1

JN.1

V-23DEC-01

4

KP.1.1

KP

V-23DEC-01

2

KP.1.2

KP

V-23DEC-01

1

KP.2

KP

V-23DEC-01

5

KP.2.1

KP

V-23DEC-01

1

KP.2.3

KP

V-23DEC-01

3

KP.3

KP

V-23DEC-01

48

KP.4.1

KP

V-23DEC-01

5

KR.1

JN.1

V-23DEC-01

1

KU.2

JN.1

V-23DEC-01

2

Unassigned

Unassigned

Unassigned

79

XDK

JN.1

V-23DEC-01

1

XDV.1

JN.1

V-23DEC-01

1

Total

-

-

192


 

6.2 Total counts and percentage sequenced by parent lineage for the last 12 months of sequencing data (05 June 2023 to 09 June 2024)

Table 6.2. Summary of variants sequenced in Northern Ireland over the past 12 months

Parent Lineage

Variant

WHO variant name

Sequence count

Percentage sequenced

Unassigned

Unassigned

 

480

25.6

JN.1

V-23DEC-01

Omicron

399

21.3

XBB

V-22OCT-02

Recombinant

307

16.4

XBB.1.16

V-23APR-01

Recombinant

243

13.0

EG.5.1

V-23JUL-01

Recombinant

163

8.7

XBB.1.5

V-23JAN-01

Recombinant

89

4.8

BA.2.86

V-23AUG-01

Omicron

87

4.6

KP

V-23DEC-01

Omicron

69

3.7

CH.1.1

V-22DEC-01

Omicron

11

0.6

Recombinant

Recombinant

Recombinant

9

0.5

BA.3

VOC-21NOV-01

Omicron

8

0.4

BA.2

VOC-22JAN-01

Omicron

7

0.4