key: cord-0941101-gw5ulk0z
authors: Butler, Dearbhla; Coyne, Dermot; Pomeroy, Louise; Williams, Pádraig; Holder, Paul; Carterson, Alex; Field, Stephen; Waters, Allison; O'Flaherty, Niamh
title: CONFIRMED CIRCULATION OF SARS-COV-2 IN IRISH BLOOD DONORS PRIOR TO FIRST NATIONAL NOTIFICATION OF INFECTION
date: 2021-11-25
journal: J Clin Virol
DOI: 10.1016/j.jcv.2021.105045
sha: 2e9e0b104ea461d8d8ef7b38dd005f703a69d9a0
doc_id: 941101
cord_uid: gw5ulk0z

INTRODUCTION: Blood donor studies offer a unique opportunity to screen healthy populations for the presence of antibodies to emerging infections. We describe the use of blood donor specimens to track the ‘first-wave’ of the COVID-19 pandemic in Ireland. METHODOLOGY: A random selection of donor samples received by the Irish Blood Transfusion Service (IBTS) between February and September 2020 (n=8,509) were screened by multiple commercial SARs-CoV-2 antibody assays. The antibody detection rate was adjusted to the population to determine the SARS-CoV-2 seroprevalence in Ireland. RESULTS: SARS-CoV-2 antibody detection rose significantly during the first peak of COVID-19 infection, increasing from 0.3% in March, to 2.9% in April (p<0.0001, The first SARS-CoV-2 antibody positive donor samples were collected on the 17(th) February 2020, 2 weeks prior to the first official notification. This is the earliest serological evidence of SARS-CoV-2 circulating in the Irish population. Our results also show a significantly higher antibody prevalence in the Capital city and in donors less than 40 years of age. CONCLUSIONS: The present study demonstrates evidence of SARS-CoV-2 antibody reactivity across all age groups and counties. The critical value of blood donor seroprevalence studies is apparent in this report which identified the earliest serological evidence of SARS-CoV-2 infection in Ireland, as well as documenting the evolution of COVID-19 pandemic in Ireland over time.

CREDIT AUTHOR STATEMENT 

This work was supported by the Irish Blood Transfusion Service internal research and development funding, and by Abbott Diagnostics. Abbott diagnostics provided reagents for testing; however, has had no involvement in study design; sample collection, analysis and interpretation of data; writing of the report; and in the decision to submit the article for publication.

The first case of SARS-CoV-2 in the Republic of Ireland was reported on February 29th 2020 in a young male tourist who had returned from Northern Italy; however it was later reported that a case of community transmission had already presented to hospital in the southern part of the country [1] [2] [3] [4] . A rapidly evolving response was demanded of Irish health services, to identify, test and quarantine cases of infection before health services became overwhelmed.

Molecular-based testing was promptly established but testing capacity was limited by reagent supply. By March 12th 2020 high level public health restrictions were imposed. Travel was permitted for essential work only and persons greater than seventy years of age were advised to 'cocoon' indoors. An easing of restrictions over the summer of 2020 heralded a resurgence of cases leading to the "2nd wave" of cases, peaking in October 2020 [1] [2] [3] [4] [5] .

The Irish Blood Transfusion Service (IBTS) responded to the emerging threat of SARS CoV-2 by introducing a 28-day deferral for those with a travel-related risk, symptoms suggestive of, or contact with known cases of COVID-19. In accordance with the evolving national guidance on a novel emerging infectious disease with an uncharacterized transfusiontransmissibility risk, restrictions remained in place at the IBTS even after it was confirmed that SARS-CoV-2 did not pose a transfusion-transmission risk [6] [7] [8] . These measures protected staff, blood donors, the blood supply and the recovering donors themselves.

It is now understood that asymptomatic COVID-19 infection occurs at a rate of 33-75% [9] [10] [11] . This is reflected in our national data which estimates that approximately 60% of those with detectable viral RNA were documented as 'symptomatic' in Irish surveillance reports.

As a result, and consistent with many infectious disease outbreaks, the full extent of the SARS-CoV-2 pandemic in Ireland is likely under-recorded [10, 12] . Blood donor studies 6 offer a unique opportunity to screen healthy populations for the presence of antibodies to new and emerging infections [13] . This is particularly relevant for COVID-19 as it is expected that blood donor behaviours, which may be associated with a lower incidence of some infections, are unlikely to be protective against a respiratory infection [14] [15] [16] [17] [18] . Furthermore, detailed seroprevalence data is essential to develop appropriate national vaccination strategies, and for the evaluation of the effectiveness of the various infection control measures.

In the present study, we describe the use of blood donor specimens to track the 'first-wave' of the COVID-19 pandemic in Ireland. Specifically, we provide evidence of the SARS-CoV-2 antibodies circulating in the Irish blood donor population prior to the first official notification of the disease. In addition, the significance of donor age, blood group and geographical location were analysed.

A random selection of blood donor plasma samples from donations received by the Irish Blood Transfusion Service (IBTS) between February and September 2020 (n=8,509) were chosen for inclusion in the study. This study was approved by the National Office for Research Ethics Committee. Irish blood donors were asymptomatic and provided consent at donation for the use of their blood samples in anonymised research. Limited demographic information was retrieved from the blood management system, eProgesa version 5.0.3, prior to anonymisation, and included gender, age, donation clinic, ABO blood group and Anti-D (RhD) status.

All samples were tested according to the study algorithm outlined in Figure 1 , and in accordance with the manufacturer's instructions, as follows: (iv) SARS-CoV-2 Total AB ELISA (Wantai, Fortress Diagnostics: Confirmatory testing of inconclusive samples was carried out following referral of samples to the National Virus Reference Laboratory (NVRL), using the Fortress Diagnostics Wantai assay . As this assay was carried out at an independent reference Laboratory and has been previously shown to have optimum sensitivity, we utilized this assay as the confirmatory assay for borderline results [19] [20] [21] . Testing was performed per manufacturer's instructions. This assay qualitatively detected IgM and IgG antibodies to SARS-CoV-2 spike protein. Samples with an index value ≥1.1 A/CO were considered positive.

Statistical analyses were performed using the statistical software package IBM SPSS Descriptive statistics are presented as percentages and numbers. The Chi-Square test and confidence intervals were used to assess associations between donor demographic variables.

A value of p<0.05 was considered statistically significant. Multivariable regression analyses were carried out, where appropriate, to control for possible gender and age confounding.

The Figure 2 ). The seroprevalence rate stabilised at 2.5-3.5% for the remainder of the study period.

Two SARS-CoV-2 seroreactive donors were identified in February 2020. Both of these samples were collected on February 17 th 2020, which is 12 days before the first official COVID-19 case was reported in the Republic of Ireland [1] [2] [3] [4] . This significant finding, in our belief, likely reflects the earliest evidence of SARS-CoV-2 infection in Ireland, and indicates that the virus was circulating prior to the first notified case on the 29 th of February. The total antibody assay was reactive in these two asymptomatic donors from February 17 th , but SARS-CoV-2 IgG was not detected by the Abbott qualitative IgG assay or the Abbott quantitative spike IgG assay. Antibody detection was confirmed by total antibody testing using the Wantai SARS-CoV-2 Total AB ELISA (Fortress Diagnostics). The two seropositive donors identified donated in geographically distinct parts of the country; one donor attended a clinic in Munster, and the other in Ulster.

As expected, antibody detection varied greatly by age group, with the highest rate of 5.3% Figure 4 ).

SARS-CoV-2 antibody detection was compared with donor demographics, including blood groups. The presence of the blood group A antigen was significantly higher in donors samples with detectable SARS-CoV-2 antibody. This difference remained significant following adjustment for possible confounding by donor age and gender (p<0.001).

Blood services can provide valuable epidemiological data on emerging infections informing policy and national surveillance programmes [16] , and can assess the dynamics of viral circulation, and model the evolution of infectious disease outbreaks, such as the COVID-19

pandemic. The first SARS-CoV-2 antibody positive donor samples were collected on the 17 th February 2020. This is the earliest serological evidence of SARS-CoV-2 circulating in the Irish population. These donations were received at sites which were in geographic proximity to the first documented case of community transmission in Ireland, and the first case diagnosed by PCR on the island of Ireland, respectively [1] [2] [3] [4] . Current evidence indicates that the IgG response to SARS-CoV-2 peaks 3 to 7 weeks post-infection. This acute antibody response is followed by a plateau phase, and subsequently slowly declines [16] . IgG was not detected in these early reactive donors. We propose these results reflect the presence of SARS-CoV-2 IgM antibody in donor plasma, suggesting that SARS-CoV-2 infection occurred within the previous two weeks in early February 2020. It is now apparent that COVID-19 was circulating in Europe earlier than first official notifications to the European Centre for Disease Prevention and Control (ECDC) [1, 4] . Retrospective PCR testing of a stored respiratory sample from a patient hospitalised in France in December 2019 confirmed SARS-CoV-2 infection [23] . The relatively high rate of asymptomatic infection has played a large part in the widespread global transmission of SARS-CoV-2.

Our study is consistent with national surveillance data which indicates that widespread community transmission did not occur before March 2020 [1] . The potential for SARS-CoV-2 IgG antibody decline was mitigated by incorporating multiple screening assays, into the donor testing algorithm [16, [24] [25] [26] . Seroprevalence rates increased significantly in April but remained stable at this level until the end of the study, possibly reflecting compliance with public health measures implemented during this time. The donor seroprevalence rate of 2.4% was higher than that reported for in the first wave of COVID-19 infections in Ireland by direct methods, confirming a higher rate of infection in the community than was diagnosed using PCR testing [1, 4] . This finding is comparable to what was observed in similar blood donor studies across Europe, such as Denmark and the Netherlands, which reported a SARS-CoV-2 donor seroprevalence of 1.9% and 3.1% between April and May 2020, respectively [17, 27] . Donor studies are extremely suitable for such international comparison as all donors are carefully pre-selected using similar guidelines [16] .

Dublin, located in the Eastern Irish province, Leinster, is the most populated city and has consistently reported the largest cumulative number of cases. However, incidence rates have been variable across the country [28] . The Study to investigate COVID-19 Infection in People Living in Ireland (SCOPI) showed significantly higher antibody prevalence in Dublin compared to the more rural Irish western province of Connaught in the summer of 2020. The results from these two locations were extrapolated to estimate an overall national seroprevalence of 1.7% (95% CI; 1.1-2.4%) [29] . Although, our estimate of overall seroprevalence falls within the confidence intervals of that calculated by the SCOPI study;

the rate is higher than previously estimated [29] . Donor samples were obtained from all 26 counties and may be more representative of the true seroprevalence. Notably, a different antibody detection temporal trend was observed for Ulster compared to the other provinces which all maintained a steady rate after the initial increase. The counties of Ulster border Northern Ireland, where public health restrictions were implemented and lifted at different times [30] . In addition, cross border movement of people may have contributed to differing levels of infection in that area.

The Irish case fatality ratio is reported as 1.86%, with the heaviest burden of COVID-19 disease and mortality in the older age groups [28] . In direct contrast to those severely impacted by COVID-19 disease, the highest rate of circulating antibodies was detected in donors less than 40 years of age, and lowest in the older age categories. Several factors may have influenced this, such as different age-related responses to public health restrictions, social behaviours, the likelihood of asymptomatic infection in younger individuals, recovery time, pre-selection of younger donors during public health restrictions and the individual risk perception surrounding blood donation during the pandemic [31] .

The impact of ABO blood group on SARS-CoV-2 susceptibility remains unclear [32] [33] [34] [35] [36] .

Blood groups are known to influence individual susceptibility to other viruses such as SARS-

CoV-1 and norovirus [34] . A significantly higher rate of seropositivity was observed in Irish donors with the blood group A antigen. Possible mechanisms for the observed difference include anti-A antibodies binding to viral antigens, resulting in a protective effect by blocking the Spike and ACE-2 protein interaction required for viral entry [36] . However, the clinical significance of this finding remains unclear and merits further study.

In conclusion, the present study of over 8,000 blood donors, sampled during the first wave of 

☐ The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

☒The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:

This work was supported by the Irish Blood Transfusion Service internal research and development funding, and by Abbott Diagnostics. Abbott diagnostics provided reagents for testing; however, has had no involvement in study design; sample collection, analysis and interpretation of data; writing of the report; and in the decision to submit the article for

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The IBTS is indebted to our dedicated donors who have continued to attend blood donor clinics during these challenging times. We also kindly acknowledge the contribution of our colleagues at the National Virus Reference Laboratory for their time and help with confirmatory SARS-CoV-2 antibody testing. We also acknowledge the contribution of Abbott Laboratories to the design and funding of the testing algorithm.