Analysis of SARS-CoV-2 antibody seroprevalence in Northern Ireland during 2020-2021

Michelle K. Greene, Peter Smyth, Andrew English, Joseph McLaughlin, Magda Bucholc, Janice Bailie, Julie McCarroll, Margaret McDonnell, Alison Watt, George Barnes, Mark Lynch, Kevan Duffin, Gerard Duffy, Claire Lewis, Jacqueline James, Alan W Stitt, Tom Ford, Maurice O'Kane, Taranjit Singh Rai, Anthony J BjoursonChristopher Cardwell, J Stuart Elborn, David S Gibson, Christopher J. Scott

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BACKGROUND: With the spread of SARS-CoV-2 impacting upon public health directly and socioeconomically, further information was required to inform policy decisions designed to limit virus spread during the pandemic. This study sought to contribute to serosurveillance work within Northern Ireland to track SARS-CoV-2 progression and guide health strategy.

METHODS: Sera/plasma samples from clinical biochemistry laboratories were analysed for anti-SARS-CoV-2 antibodies. Samples were assessed using an Elecsys anti-SARS-CoV-2 or anti-SARS-CoV-2 S ECLIA (Roche) on an automated cobas e 801 analyser. Samples were also assessed via an anti-SARS-CoV-2 ELISA (Euroimmun). A subset of samples assessed via the Elecsys anti-SARS-CoV-2 ECLIA were subsequently analysed in an ACE2 pseudoneutralisation assay using a V-PLEX SARS-CoV-2 Panel 7 for IgG and ACE2 (Meso Scale Diagnostics).

RESULTS: Across three testing rounds (June-July 2020, November-December 2020 and June-July 2021 (rounds 1-3 respectively)), 4844 residual sera/plasma specimens were assayed for anti-SARS-CoV-2 antibodies. Seropositivity rates increased across the study, peaking at 11.6 % (95 % CI 10.4 %-13.0 %) during round 3. Varying trends in SARS-CoV-2 seropositivity were noted based on demographic factors. For instance, highest rates of seropositivity shifted from older to younger demographics across the study period. In round 3, Alpha (B.1.1.7) variant neutralising antibodies were most frequently detected across age groups, with median concentration of anti-spike protein antibodies elevated in 50-69 year olds and anti-S1 RBD antibodies elevated in 70+ year olds, relative to other age groups.

CONCLUSIONS: With seropositivity rates of <15 % across the assessment period, it can be concluded that the significant proportion of the Northern Ireland population had not yet naturally contracted the virus by mid-2021.

Original languageEnglish
Article numbere24184
Number of pages11
Issue number2
Early online date22 Jan 2024
Publication statusPublished - 30 Jan 2024


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