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. 2021 Sep:198:102-105.
doi: 10.1016/j.puhe.2021.07.006. Epub 2021 Jul 20.

National population prevalence of antibodies to SARS-CoV-2 in Scotland during the first and second waves of the COVID-19 pandemic

N E Palmateer  1 , E Dickson  2 , E Furrie  3 , I Godber  4 , D J Goldberg  5 , P Gousias  2 , L Jarvis  6 , L Mathie  2 , S Mavin  7 , J McMenamin  2 , T N McNeilly  8 , P Murcia  9 , J Murray  10 , G Reid  2 , C Robertson  11 , K Templeton  12 , B von Wissmann  13 , L A Wallace  2 , C Waugh  2 , A McAuley  5
Affiliations

National population prevalence of antibodies to SARS-CoV-2 in Scotland during the first and second waves of the COVID-19 pandemic

N E Palmateer et al. Public Health. 2021 Sep.

Abstract

Objectives: Studies that measure the prevalence of antibodies to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) ('seroprevalence') are essential to understand population exposure to SARS-CoV-2 among symptomatic and asymptomatic individuals. We aimed to measure seroprevalence in the Scottish population over the course of the COVID-19 pandemic - from before the first recorded case in Scotland through to the second pandemic wave.

Study design: The study design of this study is serial cross sectional.

Methods: We tested 41,477 residual samples retrieved from primary and antenatal care settings across Scotland for SARS-CoV-2 antibodies over a 12-month period from December 2019-December 2020 (before rollout of COVID-19 vaccination). Five-weekly rolling seroprevalence estimates were adjusted for the sensitivity and specificity of the assays and weighted to reference populations. Temporal trends in seroprevalence estimates and weekly SARS-CoV-2 notifications were compared.

Results: Five-weekly rolling seroprevalence rates were 0% until the end of March, when they increased contemporaneously with the first pandemic wave. Seroprevalence rates remained stable through the summer (range: 3%-5%) during a period of social restrictions, after which they increased concurrently with the second wave, reaching 9.6% (95% confidence interval [CI]: 8.4%-10.8%) in the week beginning 28th December in 2020. Seroprevalence rates were lower in rural vs. urban areas (adjusted odds ratio [AOR]: 0.70, 95% CI: 0.61-0.79) and among individuals aged 20-39 years and 60 years and older (AOR: 0.74, 95% CI: 0.64-0.86; AOR: 0.80, 95% CI: 0.69-0.91, respectively) relative to those aged 0-19 years.

Conclusions: After two waves of the COVID-19 pandemic, less than one in ten individuals in the Scottish population had antibodies to SARS-CoV-2. Seroprevalence may underestimate the true population exposure as a result of waning antibodies among individuals who were infected early in the first wave.

Keywords: Antibodies; COVID-19; Cross sectional; SARS-CoV-2; Seroprevalence.

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Conflict of interest statement

P.M. owns shares of Astra Zeneca. The remaining authors have no competing interests to declare.

Figures

Fig. 1
Fig. 1
Comparison of (a) 5-weekly rolling SARS-CoV-2 seroprevalence by source of residual samples with (b) confirmed weekly SARS-CoV-2 PCR positives reported to Public Health Scotland. Dashed lines indicate 95% confidence intervals. SARS-CoV-2 PCR positives have been plotted against ISO week +3 on the x-axis to account for the delay between exposure to the virus (infection) and formation of antibodies (seroconversion). SARS-CoV-2, severe acute respiratory syndrome coronavirus 2.
See this image and copyright information in PMC

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