Hospitalization for child maltreatment and other types of injury during the COVID-19 pandemic.

BACKGROUND: The possibility that child maltreatment was misclassified as unintentional injury during the COVID-19 pandemic has not been evaluated. OBJECTIVE: We assessed if child maltreatment hospitalizations changed during the pandemic, and if the change was accompanied by an increase in unintentional injuries. PARTICIPANTS AND SETTING: This study included children aged 0-4 years who were admitted for maltreatment or unintentional injuries between April 2006 and March 2021 in hospitals of Quebec, Canada. METHODS: We used interrupted time series regression to estimate the effect of the pandemic on hospitalization rates for maltreatment, compared with unintentional transport accidents, falls, and mechanical force injuries. We assessed if the change in maltreatment hospitalization was accompanied by an increase in specific types of unintentional injury. RESULTS: Hospitalizations for child maltreatment decreased from 16.3 per 100,000 (95 % CI 9.1-23.4) the year before the pandemic to 13.2 per 100,000 (95 % CI 6.7-19.7) during the first lockdown. Hospitalizations for most types of unintentional injury also decreased, but injuries due to falls involving another person increased from 9.0 to 16.5 per 100,000. Hospitalization rates for maltreatment and unintentional injury remained low during the second lockdown, but mechanical force injuries involving another person increased from 3.8 to 8.1 per 100,000. CONCLUSIONS: Hospitalizations for child maltreatment may have been misclassified as unintentional injuries involving another person during the pandemic. Children admitted for these types of unintentional injuries may benefit from closer assessment to rule out maltreatment.

Evaluation of anti-nucleocapsid level variation to assess SARS-CoV-2 seroprevalence in a vaccinated population.

BACKGROUND: Serosurveys have been key to public health decision-making since the beginning of the SARS-CoV-2 pandemic. However, several studies have uncovered that vaccination blunts the anti-nucleocapsid (N) response to a subsequent infection, which hinders the ability of serologic assays (including commercial ones) to detect recent infections. We therefore developed a new analytical approach to increase the sensitivity of detection of infection in vaccinated individuals. METHODS: Two samples were obtained from 248 SARS-CoV-2-positive (PCR-confirmed), vaccinated donors: one before the infection (reference sample) and one after (test sample). All samples were tested using an in-house, anti-N enzyme-linked immunosorbent assay (ELISA) which had a sensitivity of 98.1% before the mass vaccination campaign. Instead of applying a seropositivity threshold based on a single absorbance value (i.e. conventional approach), seropositivity was determined based on the ratio between the anti-N absorbance of the test and reference samples. RESULTS: The sensitivity of the new approach to detect infection in vaccinated individuals was 95.2% using a cut-off of 1.5 for the anti-N ratio, whereas that of the conventional approach was 63.3%. CONCLUSION: The new analytical approach described herein captured a significantly greater proportion of vaccinated individuals with a known history of SARS-CoV-2 infection than the conventional approach used in most serosurveys.

Cohort profile: A Québec-based plasma donor biobank to study COVID-19 immunity (PlasCoV).

PURPOSE: The long-term humoral immunity to COVID-19 is not well understood owing to the continuous emergence of new variants of concern, the evolving vaccine-induced and infection-induced immunity, and the limited duration of follow-up in previous studies. As the sole blood service in Québec (Canada), Héma-Québec established a COVID-19-focused biobank ('PlasCoV') in April 2021. PARTICIPANTS: As of January 2022, the biobank included 86 483 plasma samples from 15 502 regular donors (age range=18-84 years, females=49.7%), for an average of 5.6 donations per donor. Nearly two-thirds (65.6%) of biobank donors made at least two donations, with many donors having provided samples prevaccination and postvaccination (3061 (19.7%)) or preinfection and postinfection (131 (0.8%)), thus allowing for longitudinal studies on vaccine-induced and infection-induced immunity. FINDINGS TO DATE: A study that used PlasCoV samples revealed that previously infected individuals who received a single dose of the BNT162b2 COVID-19 vaccine exhibited the strongest immune response. By contrast, SARS-CoV-2-naïve individuals required two vaccine doses to produce a maximal immune response. Furthermore, the results of a four-phase seroprevalence study indicated that the antinucleocapsid (N) response wanes rapidly, so that up to one-third of previously infected donors were seronegative for anti-N. FUTURE PLANS: Donations from individuals who consented to participate before 1 October 2022 will be collected up until 31 March 2023. This plasma biobank will facilitate the conduct of longitudinal studies on COVID-19 immunity, thus helping to provide valuable insights into the anti-SARS-CoV-2 immune response and its persistence, and the effects of vaccination and variants on the specificity of the anti-SARS-CoV-2 immune response.

HLA and red blood cell antigen genotyping in SARS-CoV-2 convalescent plasma donors.

Aim: More data is required regarding the association between HLA allele and red blood cell (RBC) antigen expression in regard to SARS-CoV-2 infection and COVID-19 susceptibility. Methods: ABO, RhD, 37 other RBC antigens and HLA-A, B, C, DRB1, DQB1 and DPB1 were determined using high throughput platforms in 90 Caucasian convalescent plasma donors. Results: The AB group was significantly increased (1.5×, p = 0.018) and some HLA alleles were found to be significantly overrepresented (HLA-B*44:02, C*05:01, DPB1*04:01, DRB1*04:01 and DRB1*07:01) or underrepresented (A*01:01, B51:01 and DPB1*04:02) in convalescent individuals compared with the local bone marrow registry population. Conclusion: Our study of infection-susceptible but non-hospitalized Caucasian COVID-19 patients contributes to the global understanding of host genetic factors associated with SARS-CoV-2 infection and severity.

Suicide Attempts in Children Aged 10-14 Years During the First Year of the COVID-19 Pandemic.

PURPOSE: To determine if suicide attempts increased during the first year of the pandemic among young adolescents in Quebec, Canada. METHODS: We analyzed children aged 10-14 years who were hospitalized for a suicide attempt between January 2000 and March 2021. We calculated age-specific and sex-specific suicide attempt rates and the proportion of hospitalizations for suicide attempts before and during the pandemic and compared rates with patients aged 15-19 years. We used interrupted time series regression to measure changes in rates during the first (March 2020 to August 2020) and second (September 2020 to March 2021) waves and difference-in-difference analysis to determine if the pandemic had a greater impact on girls than boys. RESULTS: Suicide attempt rates decreased for children aged 10-14 years during the first wave. However, rates increased sharply during the second wave for girls, without changing for boys. Girls aged 10-14 years had an excess of 5.1 suicide attempts per 10,000 at the start of wave 2, with rates continuing to increase by 0.6 per 10,000 every month thereafter. Compared with the prepandemic period, the increase in the proportion of girls aged 10-14 years hospitalized for a suicide attempt was 2.2% greater than that of boys during wave 2. The pattern seen in girls aged 10-14 years was not present in girls aged 15-19 years. DISCUSSION: Hospitalizations for suicide attempts among girls aged 10-14 years increased considerably during the second wave of the pandemic, compared with boys and older girls. Young adolescent girls may benefit from screening and targeted interventions to address suicidal behavior.

Impact of Covid-19 on rates of gestational diabetes in a North American pandemic epicenter.

AIMS: We assessed the impact of Covid-19 on gestational diabetes rates in Quebec, the pandemic epicenter of Canada. METHODS: We conducted a population-based study of 569,686 deliveries in Quebec between 2014 and 2021. We measured gestational diabetes rates in wave 1 (March 1, 2020-August 22, 2020) and wave 2 (August 23, 2020-March 31, 2021), compared with the prepandemic period. We used interrupted time series regression to assess changes in gestational diabetes rates during each wave, and log-binomial regression models to estimate adjusted risk ratios (RR) and 95% confidence intervals (CI) for the association of the pandemic with gestational diabetes. We identified the types of patients that contributed to the change in gestational diabetes rates using Kitagawa's decomposition. RESULTS: Gestational diabetes rates were higher during the first (13.2 per 100 deliveries) and second waves (14.3 per 100 deliveries) than during the prepandemic period (12.4 per 100 deliveries). Risk of gestational diabetes increased both in wave 1 (RR 1.05, 95% CI 1.02-1.09) and wave 2 (RR 1.14, 95% CI 1.10-1.18), compared with the prepandemic period. However, most of the increase in gestational diabetes rates was driven by low-risk women without Covid-19 infections who were socioeconomically advantaged, had no comorbidity, and were 25-34 years of age. CONCLUSIONS: Gestational diabetes rates increased during the pandemic, mainly among women traditionally at low risk of hyperglycemia who did not have Covid-19 infections. Sudden widespread changes in screening or lifestyle can have a large impact on gestational diabetes rates in a population.

How do we decide how representative our donors are for public health surveillance?

BACKGROUND: Surveillance of blood donors is fundamental to safety of the blood supply. Such data can also be useful for public health policy but tend to be underutilized. When the COVID-19 pandemic arrived, blood centers around the world measured blood donor SARS-CoV-2 seroprevalence to inform public health policy. There is now a movement toward blood centers becoming more involved in public health research and surveillance post-pandemic. However, blood donors are a healthy population and not representative of all segments of the general population. In this article, we explain how blood centers can evaluate their donor base to understand which part of the general population they are representative of. STUDY DESIGN AND METHODS: Methodologic approaches for evaluating samples relative to the target population were reviewed. Blood donor data that are available to most blood centers were identified and application to assess representativeness of blood donors was evaluated. RESULTS: Key aspects of blood donor data to compare with general population data include donor selection criteria, health indicators, geography, and demographics. In some cases, statistical adjustment can improve representativeness. DISCUSSION: Comparing key blood donor data with corresponding general population data can define the subset of the general population for which a particular blood center's donors may be representative of. We suggest that donors are an ideal convenience population for surveillance of infectious agents which are frequently asymptomatic and main routes of transmission are not deferrable, for studying the natural history of disease in an initially well population, and for vaccination serology surveillance.

COVID-19 vaccine humoral response in frequent platelet donors with plateletpheresis-associated lymphopenia.

BACKGROUND: Plateletpheresis involves platelet separation and collection from whole blood while other blood cells are returned to the donor. Because platelets are replaced faster than red blood cells, as many as 24 donations can be done annually. However, some frequent apheresis platelet donors (>20 donations annually) display severe plateletpheresis-associated lymphopenia; in particular, CD4+ T but not B cell numbers are decreased. COVID-19 vaccination thereby provides a model to assess whether lymphopenic platelet donors present compromised humoral immune responses. STUDY DESIGN AND METHODS: We assessed vaccine responses following 2 doses of COVID-19 vaccination in a cohort of 43 plateletpheresis donors with a range of pre-vaccination CD4+ T cell counts (76-1537 cells/µl). In addition to baseline T cell measurements, antibody binding assays to full-length Spike and the Receptor Binding Domain (RBD) were performed pre- and post-vaccination. Furthermore, pseudo-particle neutralization and antibody-dependent cellular cytotoxicity assays were conducted to measure antibody functionality. RESULTS: Participants were stratified into two groups: <400 CD4/µl (n = 27) and ≥ 400 CD4/µl (n = 16). Following the first dose, 79% seroconverted within the <400 CD4/µl group compared to 87% in the ≥400 CD4/µl group; all donors were seropositive post-second dose with significant increases in antibody levels. Importantly differences in CD4+ T cell levels minimally impacted neutralization, Spike recognition, and IgG Fc-mediated effector functions. DISCUSSION: Overall, our results indicate that lymphopenic plateletpheresis donors do not exhibit significant immune dysfunction; they have retained the T and B cell functionality necessary for potent antibody responses after vaccination.

Canadian blood suppliers: An expanding role in public health surveillance?

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic galvanized blood donor seroprevalence studies, which continue to inform public health policy. We propose that the two Canadian blood suppliers, Héma-Québec and Canadian Blood Services, expand their role in public health surveillance in the post-pandemic period. Together blood suppliers have near-national reach, collecting blood donations nearly every day in all larger cities and many smaller municipalities. Blood donors are a healthy subset of the general population. Demographic data, routine infectious disease testing and screening questionnaire data are collected for all donations. Close to one million blood samples per year could be made available for surveillance. With 90% repeat donors, longitudinal sampling is possible. Current blood donor surveillance includes monitoring infectious marker rates in low risk (e.g. HIV, hepatitis C virus) or asymptomatic (e.g. West Nile virus) populations, and ad hoc studies to monitor transfusion-transmissible infections. These include tick-borne infections such as Babesia microti and foodborne infections such as hepatitis E. Canadian Blood Services and Héma-Québec are actively seeking to engage with public health professionals to further develop a role in public health surveillance.

Current challenges of severe acute respiratory syndrome coronavirus 2 seroprevalence studies among blood donors: A scoping review.

BACKGROUND AND OBJECTIVES: Blood donors are increasingly being recognized as an informative resource for surveillance. We aimed to review severe acute respiratory syndrome coronavirus 2 seroprevalence studies conducted among blood donors to investigate methodological biases and provide guidance for future research. MATERIALS AND METHODS: We conducted a scoping review of peer-reviewed and preprint publications between January 2020 and January 2021. Two reviewers used standardized forms to extract seroprevalence estimates and data on methodology pertaining to population sampling, periodicity, assay characteristics, and antibody kinetics. National data on cumulative incidence and social distancing policies were extracted from publicly available sources and summarized. RESULTS: Thirty-three studies representing 1,323,307 blood donations from 20 countries worldwide were included (sample sizes ranged from 22 to 953,926 donations). The majority of the studies (79%) reported seroprevalence rates <10% (ranging from 0% to 76% [after adjusting for waning antibodies]). Overall, less than 1 in 5 studies reported standardized seroprevalence rates to reflect the demographics of the general population. Stratification by age and sex were most common (64% of studies), followed by region (48%). A total of 52% of studies reported seroprevalence at a single time point. Overall, 27 unique assay combinations were identified, 55% of studies used a single assay and only 39% adjusted seroprevalence rates for imperfect test characteristics. Among the nationally representative studies, case detection was most underrepresented in Kenya (1:1264). CONCLUSION: By the end of 2020, seroprevalence rates were far from reaching herd immunity. In addition to differences in community transmission and diverse public health policies, study designs and methodology were likely contributing factors to seroprevalence heterogeneity.

Active seeking of post-donation information to minimize a potential threat to transfusion safety: A pilot programme in the context of the COVID-19 pandemic.

BACKGROUND AND OBJECTIVES: Early in the pandemic, the transmissibility of coronavirus disease-19 (COVID-19) by transfusion was unknown. We piloted a systematic, post-donation outreach programme to contact blood donors and inquired about symptoms post-donation. MATERIALS AND METHODS: Persons who donated on on May 1 and 2, 2020 were contacted 3 days post-donation, by phone to assess COVID-19-related symptoms. Half of the donors were administered a short questionnaire, consisting of only three questions. Others were questioned using a longer, more specific questionnaire. If symptoms were reported, products were quarantined until donors were contacted again by a trained nurse who more thoroughly assessed the likelihood of COVID-19. Blood products were withdrawn if symptoms indicative of COVID-19 were identified. RESULTS: Of 654 donors, 609 (93.1%) were successfully contacted. Of 310 donors who answered the short questionnaire and 299 who answered the long questionnaire, 19 (6.1%) and 8 (2.7%) had one or more symptoms, respectively. Based on the nurses' assessment, two donations (0.3%) had to be withdrawn. CONCLUSION: These results suggest that actively seeking post-donation information might be feasible to mitigate emerging, unqualified transfusion risks.

Seroprevalence of SARS-CoV-2 antibodies among blood donors in Québec: an update from a serial cross-sectional study.

OBJECTIVES: We previously estimated the seroprevalence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies following the first pandemic wave at 2.23% in Québec, Canada. Following the much bigger second wave in fall 2020 and early 2021, we estimated the seroprevalence of anti-SARS-CoV-2 in Québec during the first months of 2021. METHODS: Blood samples from regular, asymptomatic (for ≥ 14 days) donors were collected between January 25, 2021 and March 11, 2021. Anti-SARS-CoV-2 seropositivity was assessed using an enzyme-linked immunosorbent assay that captures antibodies directed against the receptor binding domain of the SARS-CoV-2 spike (and hence cannot discriminate between infection- and vaccine-induced seropositivity). Seroprevalence estimates were adjusted for regional distribution, age, and sex. RESULTS: Samples from 7924 eligible donors were analyzed, including 620 (7.8%) vaccinated donors and 7046 (88.9%) unvaccinated donors (vaccination status unknown for 258 (3.3%) donors). Overall, median age was 51 years; 46.4% of donors were female. The adjusted seroprevalence was 10.5% (95% CI = 9.7-11.3) in the unvaccinated population and 14.7% (95% CI = 13.8-15.6) in the overall population. Seroprevalence gradually decreased with age and was higher among donors who self-identified as having a racial/ethnic background other than white, both in the overall and in the unvaccinated populations. CONCLUSION: The seroprevalence of SARS-CoV-2 antibodies significantly increased in Québec since spring 2020, with younger persons and ethnic minorities being disproportionately affected. When compared with the cumulative incidence rate reported by public health authorities (i.e., 3.3% as of March 11, 2021), these results suggest that a substantial proportion of infections remain undetected despite improvements in access to COVID-19 testing.

RéSUMé: OBJECTIFS: Lors d'une première étude, nous avons estimé la séroprévalence des anticorps contre le syndrome respiratoire aigu sévère coronavirus 2 (SRAS-CoV-2) après la première vague pandémique à 2,23 % au Québec, Canada. Cette seconde étude estime la séroprévalence de l'anti-SRAS-CoV-2 au Québec lors de la deuxième vague pandémique. MéTHODES: Des échantillons de donneurs de sang asymptomatiques (≥ 14 jours) ont été prélevés entre le 25 janvier et le 11 mars 2021. La séropositivité a été évaluée à l'aide d'un dosage immuno-enzymatique qui capture les anticorps dirigés contre la protéine Spike du récepteur de domaine de liaison du SARS-CoV-2 (et ne peut donc distinguer l'immunité induite par l'infection et la vaccination). La séroprévalence a été ajustée en fonction de l'âge et du sexe par région. RéSULTATS: Des échantillons de 7 924 donneurs ont été analysés, dont 620 (7,8 %) étaient vaccinés et 7 046 (88,9 %) étaient non vaccinés (statut vaccinal inconnu pour 258 (3,3 %) donneurs). Dans l'ensemble, l'âge médian était de 51 ans et 46,4 % des donneurs étaient des femmes. La séroprévalence ajustée était de 10,5 % (IC 95 % = 9,7 à 11,3) dans la population non vaccinée et de 14,7 % (IC 95 % = 13,8 à 15,6) dans la population globale. La séroprévalence diminuait progressivement avec l'âge et était plus élevée chez les donneurs d'origine ethnique autre que blanche. CONCLUSION: La séroprévalence anti-SRAS-CoV-2 a considérablement augmenté au Québec depuis le printemps 2020, les personnes plus jeunes et les minorités ethniques étant plus touchées. Comparés au taux d'incidence cumulatif signalé par la santé publique (c.-à-d. 3,3 % au 11 mars 2021), ces résultats suggèrent qu'une proportion importante d'infections reste non détectée.

Evidence of SARS-CoV-2 Infection in Cells, Tissues, and Organs and the Risk of Transmission Through Transplantation.

The emergence of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus responsible for the coronavirus disease 2019 (COVID-19) pandemic has raised concerns for programs overseeing donation and transplantation of cells, tissues, and organs (CTO) that this virus might be transmissible by transfusion or transplantation. Transplant recipients are considered particularly vulnerable to pathogens because of immunosuppression, and SARS-CoV-2 is likely to generate complications if contracted. Several signs and symptoms observed in COVID-19 positive patients reflect damage to multiple organs and tissues, raising the possibility of extrapulmonary SARS-CoV-2 infections and risk of transmission. At the beginning of the pandemic, a consensus has emerged not to consider COVID-19 positive patients as potential living or deceased donors, resulting in a global decrease in transplantation procedures. Medical decision-making at the time of organ allocation must consider safely alongside the survival advantages offered by transplantation. To address the risk of transmission by transplantation, this review summarizes the published cases of transplantation of cells or organs from donors infected with SARS-CoV-2 until January 2021 and assesses the current state of knowledge for the detection of this virus in different biologic specimens, cells, tissues, and organs. Evidence collected to date raises the possibility of SARS-CoV-2 infection and replication in some CTO, which makes it impossible to exclude transmission through transplantation. However, most studies focused on evaluating transmission under laboratory conditions with inconsistent findings, rendering the comparison of results difficult. Improved standardization of donors and CTO screening practices, along with a systematic follow-up of transplant recipients could facilitate the assessment of SARS-CoV-2 transmission risk by transplantation.

An international comparison of anti-SARS-COV-2 assays used for seroprevalence surveys from blood component providers.

BACKGROUND AND OBJECTIVES: Access to large pools of healthy adult donors advantageously positions blood component providers to undertake anti-SARS-CoV-2 seroprevalence studies. While numerous seroprevalence reports have been published by blood operators during the COVID-19 pandemic, details on the assay used has not been well documented. The objectives of this study were to evaluate the diversity of assays being used by blood operators and assess how this may affect seroprevalence estimates. MATERIALS AND METHODS: We surveyed 49 blood component providers from 39 countries. Questionnaire included information on the number and identity of assays used, the detected immunoglobulin(s) and target antigen, and performance characteristics (sensitivity, specificity). RESULTS: Thirty-eight of the 49 contacted blood suppliers provided at least partial responses. The results indicate that 19 commercial and five in-house serology assays have been used by surveyed blood operators. The Abbott SARS-CoV-2 IgG assay was the most commonly used kit and utilized by 15 blood suppliers. Two assays did not detect IgG, but detected either IgM/IgA or IgM. 68·2% of assays targeted the spike protein and 50% the nucleocapsid protein, while 18·2% targeted both viral proteins. The sensitivity and specificity of IgG-specific assays ranged from 71·9% to 100% and from 96·2% to 100%, respectively. As of 18 October 2020, the seroprevalence was below 5% in 10 of 14 countries reporting. CONCLUSION: Our results highlight the diversity of assays being used. Analyses comparing blood donor seroprevalence across countries should consider assay characteristics with optimization of signal/cut-off ratios and consistent methodology to adjust for waning antibody.

The estimated risk of SARS-CoV- 2 infection via cornea transplant in Canada.

In late 2019 the respiratory illness, Corona Virus Disease-19 caused by the SARS-CoV-2 virus emerged in China and quickly spread to other countries. The primary mode of transmission is person-to-person via respiratory droplets. SARS-CoV-2 has been identified in conjunctiva. Transmission by cornea transplant has not been reported but is theoretically possible. We aimed to estimate the possible risk of transmission in Canada via cornea transplant during the first wave of the pandemic, and the potential risk reduction from testing decedents. We constructed a deterministic model in which the risk of transmission was estimated as the product of three proportions: decedents with SARS-CoV-2 infection, corneas that are NAT positive, and NAT positive corneas presumed to transmit. Risk was estimated according to 3 scenarios: most likely, optimistic and pessimistic. At the peak of the first wave of the pandemic risk was estimated to be 1 in 63,031 cornea transplants in Canada but could be as low as 1 in 175,821 or as high as 1 in 10,129. It would take 16 years at the peak infection of the first wave of the pandemic to observe 1 transmission. Testing would reduce the risk of 1 in 63,031 to 1 in 210,104 assuming 70% test sensitivity. The theoretical risk of SARS-CoV-2 transmission by cornea transplant is extremely low and decedent testing is unlikely to be beneficial.

SARS-CoV-2 seroprevalence among blood donors in Québec, and analysis of symptoms associated with seropositivity: a nested case-control study.

OBJECTIVES: A substantial proportion of individuals infected with SARS-CoV-2 do not experience noticeable symptoms typical of COVID-19. Our objectives were to evaluate the impact of the first wave of the pandemic in Québec by measuring SARS-CoV-2 antibody seroprevalence in a convenience sample of healthy blood donors and to study the association between seropositivity and the occurrence of COVID-19 symptoms. METHODS: The study design was a cross-sectional serological survey with a nested case-control study. Residual blood samples from donations collected between May 25 and July 9, 2020 (well before vaccination rollout) in the province of Québec were tested for anti-Spike RBD antibodies by ELISA. Seropositive donors and a control group of seronegative donors were questioned about prior COVID-19 symptoms. All qualified blood donors were eligible for participation. RESULTS: A total of 7691 blood donors were included in the study. After adjustments, the seroprevalence rate was 2.2% (95% CI 1.9-2.6). Seropositive donors reported one or more symptoms in a proportion of 52.2% (95% CI 44.2-60.1); this proportion was 19.1% (95% CI 13.4-26.1) among seronegative donors, suggesting that approximately 50-66% of all infections were asymptomatic. Univariate analysis of associations between symptoms and seropositivity revealed that except for rhinorrhea, all symptoms were significantly associated with seropositivity. CONCLUSION: Assuming that blood donors are fairly representative of the general adult population, this study shows that less than 3% of 18-69-year-olds have been infected during the first wave of the pandemic in the province of Québec. Our data also confirm that many infections escaped detection, including a substantial proportion that were asymptomatic.

RéSUMé: OBJECTIFS: Une proportion substantielle de personnes infectées par le SRAS-CoV-2 ne présentent pas de symptômes visibles typiques de la COVID-19. Nos objectifs étaient d'évaluer l'impact de la première vague de la pandémie au Québec en mesurant la séroprévalence des anticorps anti-SRAS-CoV-2 chez les donneurs de sang en bonne santé, et d'étudier l'association entre la séropositivité et la survenue des symptômes de la COVID-19. MéTHODES: Le design de l'étude était une enquête de sérologie transversale avec une étude cas-témoins nichée dans la cohorte. Des échantillons de sang provenant de dons recueillis entre le 25 mai et le 9 juillet 2020 (bien avant le déploiement de la vaccination) dans la province de Québec ont été testés pour les anticorps anti-spicule RBD (Receptor Binding Domain) par ELISA. Les donneurs séropositifs et un groupe témoin de donneurs séronégatifs ont été interrogés sur les symptômes spécifiques à la COVID-19. Tous les donneurs qualifiés pour le don de sang étaient éligibles à participer à l'étude. RéSULTATS: Au total, 7 691 donneurs de sang ont été inclus dans l'étude. Après ajustements, le taux de séroprévalence était de 2,2 % (IC à 95% 1,9­2,6). Les donneurs séropositifs ont signalé un ou plusieurs symptômes dans une proportion de 52,2 % (IC à 95% 44,2­60,1); cette proportion était de 19,1 % (IC à 95% 13,4­26,1) parmi les donneurs séronégatifs, ce qui suggère qu'entre 50 % et 66 % de toutes les infections étaient asymptomatiques. Une analyse univariée des associations entre les symptômes et la séropositivité a révélé qu'à l'exception de la rhinorrhée, tous les symptômes étaient significativement associés à la séropositivité. CONCLUSION: En supposant que les donneurs de sang sont assez représentatifs de la population adulte générale, cette étude montre que moins de 3 % des 18­69 ans ont été infectés lors de la première vague de la pandémie dans la province du Québec. Nos données confirment également que de nombreuses infections n'ont pas fait l'objet d'un test moléculaire de dépistage, y compris une proportion importante qui était asymptomatique.

Research initiatives of blood services worldwide in response to the covid-19 pandemic.

BACKGROUND AND OBJECTIVES: While coronavirus (COVID-19) is not transfusion-transmitted, the impact of the global pandemic on blood services worldwide is complex. Convalescent plasma may offer treatment, but efficacy and safety are not established. Measuring seroprevalence in donors would inform public health policy. Here, we survey blood services around the world to assess the different research programmes related to COVID-19 planned or in progress. MATERIALS AND METHODS: Blood collection services were surveyed in June 2020 to determine whether they were participating in serosurveys or convalescent plasma collection and clinical trials. RESULTS: A total of 48 countries (77% of those contacted) responded. Seroprevalence studies are planned or in progress in 73% of countries surveyed and in all continents, including low- and middle-income countries. Most aimed to inform public health policy. Convalescent plasma programmes have been initiated around the globe (79% of surveyed), about three quarters as clinical trials in high-, middle- and low-income countries. CONCLUSION: Blood services around the world have drawn upon their operational capacity to provide much-needed seroprevalence data to inform public health. They have rapidly implemented preparation of potential treatment when few treatments are available and mostly as clinical trials. At the same time, they must continue to provide blood products for recipients despite challenges of working in a state of emergency. It is important to track and coordinate research efforts across jurisdictions to gain a composite evidence-based view that will influence future practice and preparative strategies.

High-throughput detection of antibodies targeting the SARS-CoV-2 Spike in longitudinal convalescent plasma samples.

BACKGROUND: The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus is the cause of the ongoing coronavirus disease 2019 (COVID-19) pandemic, infecting millions of people and causing more than two million deaths. The SARS-CoV-2 Spike glycoproteins mediate viral entry and represent the main target for antibody responses. Humoral responses were shown to be important for preventing and controlling infection by coronaviruses. A promising approach to reduce the severity of COVID-19 is the transfusion of convalescent plasma. However, longitudinal studies revealed that the level of antibodies targeting the receptor-binding domain (RBD) of the SARS-CoV-2 Spike declines rapidly after the resolution of the infection. STUDY DESIGN AND METHODS: To extend this observation beyond the RBD domain, we performed a longitudinal analysis of the persistence of antibodies targeting the full-length SARS-CoV-2 Spike in the plasma from 15 convalescent donors. We generated a 293T cell line constitutively expressing the SARS-CoV-2 Spike and used it to develop a high-throughput flow cytometry-based assay to detect SARS-CoV-2 Spike-specific antibodies in the plasma of convalescent donors. RESULTS AND CONCLUSION: We found that the level of antibodies targeting the full-length SARS-CoV-2 Spike declines gradually after the resolution of the infection. This decline was not related to the number of donations but strongly correlated with the decline of RBD-specific antibodies and the number of days post-symptom onset. These findings help to better understand the decline of humoral responses against the SARS-CoV-2 Spike and provide important information on when to collect plasma after recovery from active infection for convalescent plasma transfusion.

Major role of IgM in the neutralizing activity of convalescent plasma against SARS-CoV-2.

Characterization of the humoral response to SARS-CoV-2, the etiological agent of COVID-19, is essential to help control the infection. The neutralization activity of plasma from patients with COVID-19 decreases rapidly during the first weeks after recovery. However, the specific role of each immunoglobulin isotype in the overall neutralizing capacity is still not well understood. In this study, we select plasma from a cohort of convalescent patients with COVID-19 and selectively deplete immunoglobulin A, M, or G before testing the remaining neutralizing capacity of the depleted plasma. We find that depletion of immunoglobulin M is associated with the most substantial loss of virus neutralization, followed by immunoglobulin G. This observation may help design efficient antibody-based COVID-19 therapies and may also explain the increased susceptibility to SARS-CoV-2 of autoimmune patients receiving therapies that impair the production of immunoglobulin M (IgM).