During the first year of the COVID-19 pandemic, the proportion of reported cases of COVID-19 among Canadians was under 6%. Although high vaccine coverage was achieved in Canada by fall 2021, the ...Omicron variant caused unprecedented numbers of infections, overwhelming testing capacity and making it difficult to quantify the trajectory of population immunity.
Using a time-series approach and data from more than 900 000 samples collected by 7 research studies collaborating with the COVID-19 Immunity Task Force (CITF), we estimated trends in SARS-CoV-2 seroprevalence owing to infection and vaccination for the Canadian population over 3 intervals: prevaccination (March to November 2020), vaccine roll-out (December 2020 to November 2021), and the arrival of the Omicron variant (December 2021 to March 2023). We also estimated seroprevalence by geographical region and age.
By November 2021, 9.0% (95% credible interval CrI 7.3%-11%) of people in Canada had humoral immunity to SARS-CoV-2 from an infection. Seroprevalence increased rapidly after the arrival of the Omicron variant - by Mar. 15, 2023, 76% (95% CrI 74%-79%) of the population had detectable antibodies from infections. The rapid rise in infection-induced antibodies occurred across Canada and was most pronounced in younger age groups and in the Western provinces: Manitoba, Saskatchewan, Alberta and British Columbia.
Data up to March 2023 indicate that most people in Canada had acquired antibodies against SARS-CoV-2 through natural infection and vaccination. However, given variations in population seropositivity by age and geography, the potential for waning antibody levels, and new variants that may escape immunity, public health policy and clinical decisions should be tailored to local patterns of population immunity.
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.
Abstract
Population-level immune surveillance, which includes monitoring exposure and assessing vaccine-induced immunity, is a crucial component of public health decision-making during a pandemic. ...Serosurveys estimating the prevalence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies in the population played a key role in characterizing SARS-CoV-2 epidemiology during the early phases of the pandemic. Existing serosurveys provide infrastructure to continue immune surveillance but must be adapted to remain relevant in the SARS-CoV-2 vaccine era. Here, we delineate how SARS-CoV-2 serosurveys should be designed to distinguish infection- and vaccine-induced humoral immune responses to efficiently monitor the evolution of the pandemic. We discuss how serosurvey results can inform vaccine distribution to improve allocation efficiency in countries with scarce vaccine supplies and help assess the need for booster doses in countries with substantial vaccine coverage.
IVIg is widely used as an immunomodulatory therapy. We have recently demonstrated that IVIg protects against airway hyperresponsiveness (AHR) and inflammation in mouse models of allergic airways ...disease (AAD), associated with induction of Foxp3
regulatory T cells (Treg). Using mice carrying a
transgene under the control of the
promoter (DEREG mice), we demonstrate in this study that IVIg generates a de novo population of peripheral Treg (pTreg) in the absence of endogenous Treg. IVIg-generated pTreg were sufficient for inhibition of OVA-induced AHR in an Ag-driven murine model of AAD. In the absence of endogenous Treg, IVIg failed to confer protection against AHR and airway inflammation. Adoptive transfer of purified IVIg-generated pTreg prior to Ag challenge effectively prevented airway inflammation and AHR in an Ag-specific manner. Microarray gene expression profiling of IVIg-generated pTreg revealed upregulation of genes associated with cell cycle, chromatin, cytoskeleton/motility, immunity, and apoptosis. These data demonstrate the importance of Treg in regulating AAD and show that IVIg-generated pTreg are necessary and sufficient for inhibition of allergen-induced AAD. The ability of IVIg to generate pure populations of highly Ag-specific pTreg represents a new avenue to study pTreg, the cross-talk between humoral and cellular immunity, and regulation of the inflammatory response to Ags.
Semaphorins are important molecules in embryonic development and multiple semaphorins have been identified as having key roles in immune regulation. To date, there is little known about Semaphorin 4C ...(Sema4C) in immune biology. We report for the first time that Sema4C is inducible in human and murine B-cells and may be important for normal B-cell development.
Human tonsillar B-cells were studied following activation
anti-CD40 antibodies in the presence or absence of representative Th1, Th2, and regulatory cytokines. Murine B-cells from WT and Sema4C
mice were similarly stimulated. B-cell phenotyping in WT and Sema4C mutant mice was performed by flow cytometry and lymphoid architecture was studied by immunohistochemistry. Sema4C expression and synapse formation were analyzed by confocal microscopy.
Gene array studies performed on human tonsillar B-cells stimulated to produce IgE revealed that Sema4C was among the top genes expressed at 24 h, and the only semaphorin to be increased under Th2 conditions. Validation studies demonstrated that human and murine B-cells expressed Sema4C under similar conditions. Sema4C
mice had impaired maturation of B-cell follicles in spleens and associated decreases in follicular and marginal zone B-cells as well as impaired IgG and IgA production. In keeping with a potential role in maturation of B-cells, Sema4C was expressed predominantly on CD27
human B-cells. Within 72 h of B-cell activation, Sema4C was localized to one pole in a synapse-like structure, in association with F-actin, B-cell receptor, and Plexin-B2. Cell polarization was impaired in Sema4C
mice.
We have identified a novel immune semaphorin induced in human and murine B-cells under Th2 conditions. Sema4C appears to be a marker for human memory B-cells. It may be important for B-cell polarization and for the formation of normal splenic follicles.
Annual influenza vaccination is recommended for patients with rheumatoid arthritis (RA), but coverage is suboptimal. We assessed the impact of an implementation strategy in enhancing vaccination ...uptake in RA. We evaluated a multimodal implementation strategy at rheumatology clinics that included 3 approaches: patient recalls, a nurse providing vaccines, and physician reminders. We compared patient-reported vaccination rates after implementation with those reported before the implementation strategy in a nonequivalent control group. In multivariate analyses, we assessed factors potentially associated with influenza vaccine uptake. One hundred and sixteen RA patients were vaccinated during the intervention. The influenza vaccination rate in RA increased from 48.5% (65/136) before implementation to 62.6% (67/107) after implementation (difference of 14.1, 95% CI 1.5, 26.1). In multivariate analyses, older age, biologics use, and physician recommendation for vaccination were associated with influenza vaccine uptake. A multimodal intervention was associated with increased influenza vaccine coverage among RA patients. Older patients and those on biologics were more likely to be immunized against influenza. Physician’s recommendations are important to promote vaccine coverage.
Key Points
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Despite current recommendations, influenza vaccine uptake among rheumatoid arthritis (RA) patients is suboptimal.
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A multimodal implementation strategy facilitating access to influenza vaccine and raising awareness through vaccination reminders improved immunization uptake in RA.
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Physicians play a key role in promoting annual seasonal influenza vaccination.
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The reasons for vaccine hesitancy in RA should be addressed to reach a vaccination target of 80% required to reduce the burden of this preventable infection.
Intravenous immunoglobulin (IVIg) is a polyclonal immunoglobulin G preparation with potent immunomodulatory properties. The mode of action of IVIg has been investigated in multiple disease states, ...with various mechanisms described to account for its benefits. Recent data indicate that IVIg increases both the number and the suppressive capacity of regulatory T cells, a subpopulation of T cells that are essential for immune homeostasis. IVIg alters dendritic cell function, cytokine and chemokine networks, and T lymphocytes, leading to development of regulatory T cells. The ability of IVIg to influence Treg induction has been shown both in animal models and in human diseases. In this review, we discuss data on the potential mechanisms contributing to the interaction between IVIg and the regulatory T-cell compartment.
Medical charts were reviewed and blood samples were obtained for 7days PBMCs in vitro culture with complete media and aCD40(1mg/mL)± IL-4(200U/mL), IL-21(50ng/mL) or IL-4+IL-21.
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