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

Seroprevalence of SARS-CoV-2 IgG in blood donors in a teaching institute from Western part of Maharashtra

Introduction

COVID-19 is a disease caused by the severe acute respiratory syndrome coronavirus 2 that has appeared as a global pandemic in recent times. Currently, the transmission rate has slowed down significantly, but the definite pathological reason behind this is still unknown. Therefore, the prevalence of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibody must be studied to establish the relation between the rate of transmission and antibody presence.

Materials and Methods

A clinical assessment was performed to evaluate the seroprevalence of SARS-CoV-2 Immunoglobulin G (IgG) antibodies among 299 healthy volunteers in the period of February to May 2021. Serum samples were analyzed using chemiluminescent microparticle immunoassay (CMIA) technology to detect the presence of IgG antibodies.

Result

It was observed that 21% of the participants were seropositive, and 78% of the population was seronegative across the different genders. This confirmed that the generation of antibodies is independent of gender. Simultaneously, a t-test was performed that further suggested no statistical correlation between gender and seroprevalence. Moreover, a comprehensive analysis was performed to establish the relation between age and blood group with the seroprevalence. However, there was no statistical relationship found among these parameters.

Conclusion

This study assisted in examining the underlying causes of high or low seroprevalence among healthy volunteers.

Two-phase Bayesian latent class analysis to assess diagnostic test performance in the absence of a gold standard: COVID-19 serological assays as a proof of concept

BACKGROUND AND OBJECTIVES

In this proof-of-concept study, which included blood donor samples, we aimed to demonstrate how Bayesian latent class models (BLCMs) could be used to estimate SARS-CoV-2 seroprevalence in the absence of a gold standard assay under a two-phase sampling design.

MATERIALS AND METHODS

To this end, 6810 plasma samples from blood donors who resided in Québec (Canada) were collected from May to July 2020 and tested for anti-SARS-CoV-2 antibodies using seven serological assays (five commercial and two non-commercial).

RESULTS

SARS-CoV-2 seroprevalence was estimated at 0.71% (95% credible interval [CrI] = 0.53%-0.92%). The cPass assay had the lowest sensitivity estimate (88.7%; 95% CrI = 80.6%-94.7%), while the Héma-Québec assay had the highest (98.7%; 95% CrI = 97.0%-99.6%).

CONCLUSION

The estimated low seroprevalence (which indicates a relatively limited spread of SARS-CoV-2 in Quebec) might change rapidly-and this tool, developed using blood donors, could enable a rapid update of the prevalence estimate in the absence of a gold standard. Further, the present analysis illustrates how a two-stage BLCM sampling design, along with blood donor samples, can be used to estimate the performance of new diagnostic tests and inform public health decisions regarding a new or emerging disease for which a perfect reference standard does not exist.

The changing profile of SARS-CoV-2 serology in Irish blood donors

Background

The present study aimed to investigate the progression of the SARS-CoV-2 pandemic in Ireland over the first three waves of infection.

Method

A selection of blood donor serum samples collected between February 2020 and December 2021 were analysed by various commercially available serological assays for antibodies to SARS-CoV-2 (n = 15,066).

Results

An increase in seropositivity was observed between wave 1 (February to September 2020) and wave 2 (November and December 2020) of 2.20% to 3.55%. A large increase in estimated seroprevalence to 11.89% was observed in samples collected in February and March 2021 (wave 3 of infection).The rate of seropositivity varied by age group, with the highest rate observed in the youngest donors (18-29 years) peaking at 18.79% in wave 3. The results of spike antibody (anti-S) testing indicated that 44/1009 (4.36%) of seroreactive donors in wave 3 had a serological profile consistent with vaccination. By November 2021, we detected an overall seropositivity of 97.04%.

Conclusions

The present study provides a comprehensive estimation of the level of circulating SARS-CoV-2 antibodies in Irish blood donors, enabling differentiation between vaccination and natural infection, as well as real-time monitoring of the progression of the COVID-19 pandemic in Ireland. Seroepidemiology has a role in determining reliable estimates of transmission, infection fatality rates and vaccine uptake. The continued screening of blood donors for this purpose has the potential to generate important data to assist with the management of future waves of SARS-CoV-2.

Canadian SARS-CoV-2 serological survey using antenatal serum samples: a retrospective seroprevalence study

BACKGROUND

Insufficient data on the rate and distribution of SARS-CoV-2 infection in Canada has presented a substantial challenge to the public health response to the COVID-19 pandemic. Our objective was to assess SARS-CoV-2 seroprevalence in a representative sample of pregnant people throughout Canada, across multiple time points over 2 years of the pandemic, to describe the seroprevalence and show the ability of this process to provide prevalence estimates.

METHODS

This Canadian retrospective serological surveillance study used existing serological prenatal samples across 10 provinces over multiple time periods: Feb. 3-21, 2020; Aug. 24-Sept. 11, 2020; Nov. 16-Dec. 4, 2020; Nov. 15-Dec. 3, 2021; and results from the province of British Columbia during a period in which the SARS-CoV-2 B.1.1.529 (Omicron) variant was predominant, from Nov. 15, 2021, to June 11, 2022. Age and postal code administrative data allowed for comparison with concurrent polymerase chain reactivity (PCR)-positive results collected by Statistics Canada and the Canadian Surveillance of COVID-19 in Pregnancy (CANCOVID-Preg) project.

RESULTS

Seropositivity in antenatal serum as early as February 2020 indicates SARS-CoV-2 transmission before the World Health Organization's declaration of the pandemic. Seroprevalence in our sample of pregnant people was 1.84 to 8.90 times higher than the recorded concurrent PCR-positive prevalence recorded among females aged 20-49 years in November-December 2020. Overall seropositivity in our sample of pregnant people was low at the end of 2020, increasing to 15% in 1 province by the end of 2021. Seroprevalence among pregnant people in BC during the Omicron period increased from 5.8% to 43% from November 2021 to June 2022.

INTERPRETATION

These results indicate widespread vulnerability to SARS-CoV-2 infection before vaccine availability in Canada. During the time periods sampled, public health tracking systems were under-reporting infections, and seroprevalence results during the Omicron period indicate extensive community spread of SARS-CoV-2 infection.

Cross-Canada Variability in Blood Donor SARS-CoV-2 Seroprevalence by Social Determinants of Health

We compared the seroprevalence of SARS-CoV-2 anti-nucleocapsid antibodies in blood donors across Canadian regions in 2021. The seroprevalence was the highest in Alberta and the Prairies, and it was so low in Atlantic Canada that few correlates were observed. Being male and of young age were predictive of seropositivity. Racialization was associated with higher seroprevalence in British Columbia and Ontario but not in Alberta and the Prairies. Living in a materially deprived neighborhood predicted higher seroprevalence, but it was more linear across quintiles in Alberta and the Prairies, whereas in British Columbia and Ontario, the most affluent 60% were similarly low and the most deprived 40% similarly elevated. Living in a more socially deprived neighborhood (more single individuals and one parent families) was associated with lower seroprevalence in British Columbia and Ontario but not in Alberta and the Prairies. These data show striking variability in SARS-CoV-2 seroprevalence across regions by social determinants of health. IMPORTANCE Canadian blood donors are a healthy adult population that shows clear disparities associated with racialization and material deprivation. This underscores the pervasiveness of the socioeconomic gradient on SARS-CoV-2 infections in Canada. We identify regional differences in the relationship between SARS-CoV-2 seroprevalence and social determinants of health. Cross-Canada studies, such as ours, are rare because health information is under provincial jurisdiction and is not available in sufficient detail in national data sets, whereas other national seroprevalence studies have insufficient sample sizes for regional comparisons. Ours is the largest seroprevalence study in Canada. An important strength of our study is the interpretation input from a public health team that represented multiple Canadian provinces. Our blood donor seroprevalence study has informed Canadian public health policy at national and provincial levels since the start of the SARS-CoV-2 pandemic.

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.

Seroprevalence of COVID-19 in Blood Donors: A Systematic Review and Meta-Analysis

Introduction

Determining the prevalence of SARS-CoV-2 in blood donors makes the control of virus circulation possible in healthy people and helps implement strategies to reduce virus transmission. The purpose of the study was to examine the seroprevalence of COVID-19 in blood donors using systematic review and meta-analysis.

Materials and Methods

The electronic databases PubMed, Scopus, Web of Science, and the Google Scholar search engine were searched using standard keywords up to 2022-04-26. The variance of each study was calculated according to the binomial distribution. Studies were combined according to the sample size and variance. Q Cochrane test and I2 index were used to examine the heterogeneity of the studies. Data analysis was performed in STATA 14 software, and the significance level of the tests was P < 0.05.

Results

In the 28 papers examined with 227894 samples, the seroprevalence of COVID-19 in blood donors was 10% (95% CI: 9%, 11%), estimated 5% (95% CI: 4%, 7%) among men and 6% (95% CI: 4%, 7%) among women. This rate in different blood groups was as follows: A 12% (95% CI: 10%-14%), B 12% (95% CI: 10%-15%), AB 9% (95% CI: 7%-12%), and O 13% (95% CI: 11%-16%). The seroprevalence of COVID-19 in blood donors in North America 10%, Europe 7%, Asia 23%, South America 5%, and Africa was 4%; Moreover, the seroprevalence of IgG antibodies was estimated to be 23% (95% CI: 18%-29%) and IgM 29% (95% CI: 9%-49%).

Conclusion

The highest prevalence of COVID-19 serum in women blood donors was among blood group O and Asia. The seroprevalence of IgG and IgM antibodies was high too.

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.

Supplementary Information

The online version contains supplementary material available at 10.17269/s41997-022-00622-y.

Changing Patterns of SARS-CoV-2 Seroprevalence among Canadian Blood Donors during the Vaccine Era

We monitored the seroprevalence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nucleocapsid (anti-N; proxy of natural infection) and spike protein (anti-S; proxy for humoral immunity) antibodies in blood donors across Canada from January to November 2021. The first and second doses of vaccine were deployed over this time. Anti-N seroprevalence remained low overall (about 5% or lower) from January to November but was higher in racialized groups, younger age groups, and those living in materially deprived neighborhoods. Anti-S seroprevalence corresponded with the roll out of vaccines across the country, increasing in April in older donors and then progressively to younger age groups consistent with vaccination policies targeting oldest to youngest. By November, close to 100% of blood donors were positive for anti-S. Anti-S concentrations peaked by July and began waning by September to November particularly in older donors. These data have informed national and provincial public health policy in Canada throughout vaccination rollout.

IMPORTANCE Throughout the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic, our blood donor seroprevalence study has informed Canadian public health policy at national and provincial levels. We describe the only continuously running national seroprevalence study in Canada, which spans the full length of the pandemic and per capita is one of the largest programs in the world. The benefit of seroprevalence studies is that they identify a broad range of asymptomatic and symptomatic infection histories that may not be identified with active SARS-CoV-2 nucleic acid testing programs or when case definitions change. As vaccination was deployed in Canada, we estimated the proportion of donors with vaccine-related antibodies and developed population-level estimates of SARS-CoV-2 spike antibody concentrations. Monthly predictive mathematical models and our results engaged public health organizations in new ways. In the future, we intend to continue to expand on these interactions with provincial and national public health teams.

Positive anti-SARS-CoV-2 rapid serological test results among asymptomatic blood donors

OBJECTIVES

The world is fighting with a COVID-19 pandemic, some of the uncertainties have been revealed. To figure out an estimation of asymptomatic patients and seropositive SARS-COV-2 blood donors in Iran, a national survey was conducted to find the prevalence of asymptomatic blood donors with positive SARS-COV-2 IgM/IgG test results at the end of May 2020.

MATERIAL AND METHODS

From all 31 provinces, 1339 blood donors were included. At first, data was collected with an interview containing demographic data, risk factors and possible signs and symptoms held for each donor by a trained medical expert. Then, SARS-COV-2 serologic rapid tests were conducted. Subsequently, the test results were observed and recorded; all of their photos were checked by one single expert. We corrected the prevalence rates for sensitivity and weighted them by the last year rate of blood donation of each province.

RESULTS

The corrected prevalence rates of positive serological test results for sensitivity in provinces were between zero and 38.24%. The national prevalence was calculated 14.45% after weighting. Out of 161 positive donors, only 43 cases reported related signs or symptoms during the defined period of time, while 118 (73.29%) seropositive cases had not reported any related signs or symptoms. Some signs or symptoms were reported more frequent in the SARS-COV-2 serologic rapid test positives. The highest OR (10.19) was linked to ageusia.

CONCLUSIONS

This study has shown the prevalence of seropositive results to be around 14% in target population in which around ¾ had not reported any signs or symptoms.

COVID-19 Seroprevalence in Canada Modelling Waning and Boosting COVID-19 Immunity in Canada a Canadian Immunization Research Network Study

COVID-19 seroprevalence changes over time, with infection, vaccination, and waning immunity. Seroprevalence estimates are needed to determine when increased COVID-19 vaccination coverage is needed, and when booster doses should be considered, to reduce the spread and disease severity of COVID-19 infection. We use an age-structured model including infection, vaccination and waning immunity to estimate the distribution of immunity to COVID-19 in the Canadian population. This is the first mathematical model to do so. We estimate that 60-80% of the Canadian population has some immunity to COVID-19 by late Summer 2021, depending on specific characteristics of the vaccine and the waning rate of immunity. Models results indicate that increased vaccination uptake in age groups 12-29, and booster doses in age group 50+ are needed to reduce the severity COVID-19 Fall 2021 resurgence.

Seroprevalence of SARS-CoV-2 Antibodies Among Children in School and Day Care in Montreal, Canada

IMPORTANCE

Quebec prioritized in-person learning after the first wave of the COVID-19 pandemic, with school closures being implemented temporarily in selected schools or in hot-spot areas. Quebec's decision to keep most schools open was controversial, especially in Montreal, which was the epicenter of Canada's first and second waves; therefore, understanding the extent to which children were infected with SARS-CoV-2 provides important information for decisions about school closures.

OBJECTIVE

To estimate the seroprevalence of SARS-CoV-2 antibodies in children and teenagers in 4 neighborhoods of Montreal, Canada.

DESIGN, SETTING, AND PARTICIPANTS

This cohort study (the Enfants et COVID-19: Étude de séroprévalence [EnCORE] study) enrolled a convenience sample of children aged 2 to 17 years between October 22, 2020, and March 22, 2021, in Montreal, Canada.

EXPOSURES

Potential exposure to SARS-CoV-2.

MAIN OUTCOMES AND MEASURES

The main outcome was seroprevalence of SARS-CoV-2 antibodies, collected using dried blood spots (DBSs) and analyzed with a research-based enzyme-linked immunosorbent assay (ELISA). Parents also completed an online questionnaire that included questions on self-reported COVID-19 symptoms and tests, along with sociodemographic questions.

RESULTS

This study included 1632 participants who provided a DBS sample from 30 day cares, 22 primary schools, and 11 secondary schools. The mean (SD) age of the children who provided a DBS sample was 9.0 (4.4) years; 801 (49%) were female individuals, with 354 participants (22%) from day cares, 725 (44%) from primary schools, and 553 (34%) from secondary schools. Most parents had at least a bachelor's degree (1228 [75%]), and 210 (13%) self-identified as being a racial or ethnic minority. The mean seroprevalence was 5.8% (95% CI, 4.6%-7.0%) but increased over time from 3.2% (95% CI, 0.7%-5.8%) in October to November 2020 to 8.4% (95% CI, 4.4%-12.4%) in March to April 2021. Of the 95 children with positive SARS-CoV-2 antibody results, 78 (82%) were not tested or tested negative with reverse transcription-polymerase chain reaction (RT-PCR) testing, and all experienced mild (49 [52%]) or no clinical symptoms (46 [48%]). The children of parents who self-identified as belonging to a racial and ethnic minority group were more likely to be seropositive compared with children of White parents (adjusted seroprevalence ratio, 1.9; 95% CI, 1.1-2.6).

CONCLUSIONS AND RELEVANCE

These results provide a benchmark of the seroprevalence status in Canadian children. The findings suggest that there was more transmission occurring in children compared with what was being detected by RT-PCR, although children experienced few or mild symptoms. It will be important to continue monitoring the serological status of children, particularly in the context of new COVID-19 variants of concern and in the absence of mass vaccination campaigns targeting young children.

Sero-prevalence of SARS-CoV-2 antibodies in blood donors during the third wave of infection in Norway, winter/spring 2021

Cross-sectional studies of the prevalence of anti-SARS-CoV-2 in representative groups are routinely used for surveillance of public health in Norway. The group of blood donors is easily accessible to provide an estimate over the infection prevalence. Repeated testing of returning donors also generates data about the duration of the antibody response following infection and vaccination. The aim of the current study was to provide updated information about the development of the pandemic in the blood donor population, and to estimate the number of asymptomatic donors visiting the blood center, in an effort to evaluate the measures to prevent virus spreading between donors and staff. In the two main blood banks in the Oslo area, all blood donors were offered antibody testing for a period of three months. Almost 12,000 donors were tested, and the mean weekly prevalence of antibody positive donors due to infection was 2.7 % (varied from 2.1 to 4.0 %). The number of donors presenting following vaccination was 810 (6.9 %). An average of 38 % of the infections had been asymptomatic, and 31 % of the antibody-positive donors were unaware of having been infected. In conclusion, the proportion of blood donors seropositive for anti-SARS-CoV-2 in our blood centers was stable whereas the number of vaccinated blood donors rapidly increased. This indicates that the virus spreading in the third wave of infection in the Oslo area mainly happened in groups underrepresented as blood donors. Health care workers prioritized for early vaccination may be overrepresented in the study period.