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An important aspect of microbiological surveillance is the ability to access live viruses for microneutralization assays, which enables the study of viral characteristics and mechanisms in vitro and production of positive controls for diagnostic methods. During the COVID-19 pandemic, the Public Health Agency of Sweden established a protocol for the rapid collection of clinical samples and subsequent isolation of novel virus variants. [ABSTRACT FROM AUTHOR]

Emerging data show a rapid increase in the prevalence of SARS-CoV-2 infection linked to an increase in COVID-19 cases, which is being driven by the SARS-CoV-2 Omicron variant. Compared with [...]

Background: More than a year after recovering from COVID-19, a large proportion of individuals, many of whom work in the healthcare sector, still report olfactory dysfunctions. However, olfactory dysfunction was common already before the COVID-19 pandemic, making it necessary to also consider the existing baseline prevalence of olfactory dysfunction. To establish the adjusted prevalence of COVID-19 related olfactory dysfunction, we assessed smell function in healthcare workers who had contracted COVID‐19 during the first wave of the pandemic using psychophysical testing. Methods: Participants were continuously tested for SARS‐CoV‐2 IgG antibodies since the beginning of the pandemic. To assess the baseline rate of olfactory dysfunction in the population and to control for the possibility of skewed recruitment of individuals with prior olfactory dysfunction, consistent SARS-CoV‐2 IgG naïve individuals were tested as a control group. Results: Fifteen months after contracting COVID‐19, 37% of healthcare workers demonstrated a quantitative reduction in their sense of smell, compared to only 20% of the individuals in the control group. Fifty-one percent of COVID‐19‐recovered individuals reported qualitative symptoms, compared to only 5% in the control group. In a follow-up study 2.6 years after COVID-19 diagnosis, 24% of all tested recovered individuals still experienced parosmia. Conclusions: In summary, 65% of healthcare workers experienced parosmia/hyposmia 15 months after contracting COVID-19. When compared to a control group, the prevalence of olfactory dysfunction in the population increased by 41 percentage points. Parosmia symptoms were still lingering two-and-a half years later in 24% of SARS-CoV-2 infected individuals. Given the amount of time between infection and testing, it is possible that the olfactory problems may not be fully reversible in a plurality of individuals. [ABSTRACT FROM AUTHOR]

Introduction: Several novel vaccine platforms aim at mucosal immunity in the respiratory tract to block SARS-CoV-2 transmission. Standardized methods for mucosal sample collection and quantification of mucosal antibodies are therefore urgently needed for harmonized comparisons and interpretations across mucosal vaccine trials and real-world data. Methods: Using commercial electrochemiluminescence antibody panels, we compared SARS-CoV-2 spike-specific IgA and IgG in paired saliva, nasal secretions, and serum from 1048 healthcare workers with and without prior infection. Results: Spike-specific IgA correlated well in nasal secretions and saliva (r>0.65, p<0.0001), but the levels were more than three-fold higher in nasal secretions as compared to in saliva (p<0.01). Correlations between the total population of spike-specific IgA and spike-specific secretory IgA (SIgA) were significantly stronger (p<0.0001) in nasal secretions (r=0.96, p<0.0001) as opposed to in saliva (r=0.77, p<0.0001), and spike-specific IgA correlated stronger (p<0.0001) between serum and saliva (r=0.73, p<0.001) as opposed to between serum and nasal secretions (r=0.54, p<0.001), suggesting transudation of monomeric spike specific IgA from the circulation to saliva. Notably, spike-specific SIgA had a markedly higher SARS-CoV-2 variant cross-binding capacity as compared to the total population of spike specific IgA and IgG in both nasal secretions, saliva and serum, (all p<0.0001), which emphasizes the importance of taking potential serum derived monomeric IgA into consideration when investigating mucosal immune responses. Discussion: Taken together, although spike-specific IgA can be reliably measured in both nasal secretions and saliva, our findings imply an advantage of higher levels and likely also a larger proportion of SIgA in nasal secretions as compared to in saliva. We further corroborate the superior variant cross-binding capacity of SIgA in mucosal secretions, highlighting the potential protective benefits of a vaccine targeting the upper respiratory tract. [ABSTRACT FROM AUTHOR]

Patients with chronic kidney disease (CKD) are at high risk of severe complications from COVID‐19 and functional monocyte disturbances have been implicated to play a role. Our objective was to analyse the association between kidney function and monocyte modulatory factors, with risk of mortality in patients with COVID‐19. Hospitalized patients with COVID‐19 (n = 110) were included and in‐hospital mortality was analysed with unadjusted and adjusted multiple logistic regression analysis. Plasma levels of monocyte chemoattractant factors (MIP‐1α, MCP‐1, IL‐6) and a monocyte immune modulator (sCD14) were analysed and correlated to kidney function and risk of mortality. Monocyte modulatory factors were also determined in CKD patients without infection (disease controls) and in healthy subjects. Patients who died in hospital were more often in CKD stages 3‐5, with lower estimated glomerular filtration rate (eGFR) and had significantly higher MIP‐1α and IL‐6 levels than survivors. In multiple regression analyses adjusted for age, sex and eGFR, both high MCP‐1 and high MIP‐1α were significantly associated with risk of in‐hospital mortality. Apart from impaired kidney function, also the concentrations of MCP‐1 and MIP‐1α add important prognostic information in hospitalized patients with COVID‐19. These data provide an increased understanding of the impact of monocyte modulators in patients with COVID‐19 and normal or impaired kidney function, and warrant consideration in the pursuit of new effective therapies. [ABSTRACT FROM AUTHOR]

Objective: To determine the long‐term impact of prior SARS‐CoV‐2 infection on immune responses after COVID‐19 vaccination. Methods: Using longitudinally collected blood samples from the COMMUNITY study, we determined binding (WHO BAU mL−1) and neutralising antibody titres against ten SARS‐CoV‐2 variants over 7 months following BNT162b2 in SARS‐CoV‐2‐recovered (n = 118) and SARS‐CoV‐2‐naïve (n = 289) healthcare workers with confirmed prior SARS‐CoV‐2 infection. A smaller group with (n = 47) and without (n = 60) confirmed prior SARS‐CoV‐2 infection receiving ChAdOx1 nCoV‐19 was followed for 3 months. SARS‐CoV‐2‐specific memory T‐cell responses were investigated in a subset of SARS‐CoV‐2‐naïve and SARS‐CoV‐2‐recovered vaccinees. Results: Vaccination with both vaccine platforms resulted in substantially enhanced T‐cell responses, anti‐spike IgG responses and neutralising antibodies effective against ten SARS‐CoV‐2 variants in SARS‐CoV‐2‐recovered participants as compared to SARS‐CoV‐2‐naïve participants. The enhanced immune responses sustained over 7 months following vaccination. Conclusion: These findings imply that prior SARS‐CoV‐2 infection should be taken into consideration when planning booster doses and design of current and future COVID‐19 vaccine programmes. [ABSTRACT FROM AUTHOR]

Background: Cellular immune memory responses post coronavirus disease 2019 (COVID‐19) have been difficult to assess due to the risks of contaminating the immune response readout with memory responses stemming from previous exposure to endemic coronaviruses. The work herein presents a large‐scale long‐term follow‐up study investigating the correlation between symptomology and cellular immune responses four to five months post seroconversion based on a unique severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2)‐specific peptide pool that contains no overlapping peptides with endemic human coronaviruses. Methods: Peptide stimulated memory T cell responses were assessed with dual interferon‐gamma (IFNγ) and interleukin (IL)‐2 Fluorospot. Serological analyses were performed using a multiplex antigen bead array. Results: Our work demonstrates that long‐term SARS‐CoV‐2‐specific memory T cell responses feature dual IFNγ and IL‐2 responses, whereas cross‐reactive memory T cell responses primarily generate IFNγ in response to SARS‐CoV‐2 peptide stimulation. T cell responses correlated to long‐term humoral immune responses. Disease severity as well as specific COVID‐19 symptoms correlated with the magnitude of the SARS‐CoV‐2‐specific memory T cell response four to five months post seroconversion. Conclusion: Using a large cohort and a SARS‐CoV‐2‐specific peptide pool we were able to substantiate that initial disease severity and symptoms correlate with the magnitude of the SARS‐CoV‐2‐specific memory T cell responses. [ABSTRACT FROM AUTHOR]

Objective: To develop and validate a prognostic model for in-hospital mortality after four days based on age, fever at admission and five haematological parameters routinely measured in hospitalized Covid-19 patients during the first four days after admission. Methods: Haematological parameters measured during the first 4 days after admission were subjected to a linear mixed model to obtain patient-specific intercepts and slopes for each parameter. A prediction model was built using logistic regression with variable selection and shrinkage factor estimation supported by bootstrapping. Model development was based on 481 survivors and 97 non-survivors, hospitalized before the occurrence of mutations. Internal validation was done by 10-fold cross-validation. The model was temporally-externally validated in 299 survivors and 42 non-survivors hospitalized when the Alpha variant (B.1.1.7) was prevalent. Results: The final model included age, fever on admission as well as the slope or intercept of lactate dehydrogenase, platelet count, C-reactive protein, and creatinine. Tenfold cross validation resulted in a mean area under the receiver operating characteristic curve (AUROC) of 0.92, a mean calibration slope of 1.0023 and a Brier score of 0.076. At temporal-external validation, application of the previously developed model showed an AUROC of 0.88, a calibration slope of 0.95 and a Brier score of 0.073. Regarding the relative importance of the variables, the (apparent) variation in mortality explained by the six variables deduced from the haematological parameters measured during the first four days is higher (explained variation 0.295) than that of age (0.210). Conclusions: The presented model requires only variables routinely acquired in hospitals, which allows immediate and wide-spread use as a decision support for earlier discharge of low-risk patients to reduce the burden on the health care system. Clinical Trial Registration: Austrian Coronavirus Adaptive Clinical Trial (ACOVACT); ClinicalTrials.gov, identifier NCT04351724. [ABSTRACT FROM AUTHOR]

Current SARS-CoV-2 serological assays generate discrepant results, and the longitudinal characteristics of antibodies targeting various antigens after asymptomatic to mild COVID-19 are yet to be established. This longitudinal cohort study including 1965 healthcare workers, of which 381 participants exhibited antibodies against the SARS-CoV-2 spike antigen at study inclusion, reveal that these antibodies remain detectable in most participants, 96%, at least four months post infection, despite having had no or mild symptoms. Virus neutralization capacity was confirmed by microneutralization assay in 91% of study participants at least four months post infection. Contrary to antibodies targeting the spike protein, antibodies against the nucleocapsid protein were only detected in 80% of previously anti-nucleocapsid IgG positive healthcare workers. Both anti-spike and anti-nucleocapsid IgG levels were significantly higher in previously hospitalized COVID-19 patients four months post infection than in healthcare workers four months post infection (p = 2*10−23 and 2*10−13 respectively). Although the magnitude of humoral response was associated with disease severity, our findings support a durable and functional humoral response after SARS-CoV-2 infection even after no or mild symptoms. We further demonstrate differences in antibody kinetics depending on the antigen, arguing against the use of the nucleocapsid protein as target antigen in population-based SARS-CoV-2 serological surveys. [ABSTRACT FROM AUTHOR]

Background: Emerging data support detectable immune responses for months after severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) infection and vaccination, but it is not yet established to what degree and for how long protection against reinfection lasts. Methods: We investigated SARS‐CoV‐2‐specific humoral and cellular immune responses more than 8 months post‐asymptomatic, mild and severe infection in a cohort of 1884 healthcare workers (HCW) and 51 hospitalized COVID‐19 patients. Possible protection against SARS‐CoV‐2 reinfection was analyzed by a weekly 3‐month polymerase chain reaction (PCR) screening of 252 HCW that had seroconverted 7 months prior to start of screening and 48 HCW that had remained seronegative at multiple time points. Results: All COVID‐19 patients and 96% (355/370) of HCW who were anti‐spike IgG positive at inclusion remained anti‐spike IgG positive at the 8‐month follow‐up. Circulating SARS‐CoV‐2‐specific memory T cell responses were detected in 88% (45/51) of COVID‐19 patients and in 63% (233/370) of seropositive HCW. The cumulative incidence of PCR‐confirmed SARS‐CoV‐2 infection was 1% (3/252) among anti‐spike IgG positive HCW (0.13 cases per 100 weeks at risk) compared to 23% (11/48) among anti‐spike IgG negative HCW (2.78 cases per 100 weeks at risk), resulting in a protective effect of 95.2% (95% CI 81.9%–99.1%). Conclusions: The vast majority of anti‐spike IgG positive individuals remain anti‐spike IgG positive for at least 8 months regardless of initial COVID‐19 disease severity. The presence of anti‐spike IgG antibodies is associated with a substantially reduced risk of reinfection up to 9 months following asymptomatic to mild COVID‐19. [ABSTRACT FROM AUTHOR]

The main entry receptor of severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) is angiotensin‐converting enzyme 2 (ACE2). SARS‐CoV‐2 interactions with ACE2 may increase ectodomain shedding but consequences for the renin‐angiotensin system and pathology in Coronavirus disease 2019 (COVID‐19) remain unclear. We measured soluble ACE2 (sACE2) and sACE levels by enzyme‐linked immunosorbent assay in 114 hospital‐treated COVID‐19 patients compared with 10 healthy controls; follow‐up samples after four months were analyzed for 58 patients. Associations between sACE2 respectively sACE and risk factors for severe COVID‐19, outcome, and inflammatory markers were investigated. Levels of sACE2 were higher in COVID‐19 patients than in healthy controls, median 5.0 (interquartile range 2.8–11.8) ng/ml versus 1.4 (1.1–1.6) ng/ml, p <.0001. sACE2 was higher in men than women but was not affected by other risk factors for severe COVID‐19. sACE2 decreased to 2.3 (1.6–3.9) ng/ml at follow‐up, p <.0001, but remained higher than in healthy controls, p =.012. sACE was marginally lower during COVID‐19 compared with at follow‐up, 57 (45–70) ng/ml versus 72 (52–87) ng/ml, p =.008. Levels of sACE2 and sACE did not differ depending on survival or disease severity. sACE2 during COVID‐19 correlated with von Willebrand factor, factor VIII and D‐dimer, while sACE correlated with interleukin 6, tumor necrosis factor α, and plasminogen activator inhibitor 1. Conclusions: sACE2 was transiently elevated in COVID‐19, likely due to increased shedding from infected cells. sACE2 and sACE during COVID‐19 differed in correlations with markers of inflammation and endothelial dysfunction, suggesting release from different cell types and/or vascular beds. [ABSTRACT FROM AUTHOR]

Numerous assays evaluating serological and cellular responses have been developed to characterize immune responses against SARS-CoV-2. Serological assays are both cost- and time-effective compared to cellular assays, but cellular immune responses may provide a diagnostic value to determine previous SARS-CoV-2 infection in seronegative individuals. However, potential cross-reactive T cell responses stemming from prior encounters with human coronaviruses (HCoVs) may affect assay specificity. In this study, we evaluated the specificity and sensitivity of a SARS-CoV-2 IFN-γ Release Assay (IGRA) based on the FluoroSpot method employing commercially available SARS-CoV-2-specific peptide pools, as well as an in-house designed SARS-CoV-2 peptide pool restricted to 5 amino acid stretches or less aligning with endemic HCoVs. Blood samples were obtained from healthcare workers (HCW) 5–6 months post SARS-CoV-2 spike (S) IgG and nucleocapsid (N) IgG dual seroconversion (n = 187) and HCW who had been S IgG and N IgG dual seronegative at repeated occasions, including the current sampling time point (n = 102). In addition, samples were obtained 4 to 5 months post infection from 55 polymerase chain reaction (PCR)-confirmed COVID-19 patients. Assay specificity and sensitivity were calculated with serology as a reference standard for HCW. The in-house generated peptide pool displayed a specificity of 96.1%, while the commercially available peptide pools displayed specificities of 80.4% and 85.3%, respectively. Sensitivity was higher in a cohort of previously hospitalized COVID-19 patients (96.4% and 84.0% for the commercially available peptide pools and 92.7% for the in-house generated peptide pool) compared to the HCW cohort (92.0% and 66.8% for the commercially available peptide pools and 76.0% for the in-house generated peptide pool). Based on these findings, the individual diagnostic value of T cell immune responses against SARS-CoV-2 currently appears to be limited but remain an important research tool ahead. [ABSTRACT FROM AUTHOR]

Neutrophil extracellular traps (NETs) are web-like structures consisting of DNA, histones and granule proteins, released from neutrophils in thrombus formation, inflammation, and cancer. We asked if plasma levels of the NET markers myeloperoxidase (MPO)-DNA and citrullinated histone H3 (H3Cit)-DNA, are elevated in liver cirrhosis and hepatocellular carcinoma (HCC) and if the levels correlate with clinical parameters. MPO-DNA, H3Cit-DNA, and thrombin–antithrombin (TAT) complex, as a marker of coagulation activity, were measured using ELISA in plasma from 82 patients with HCC, 95 patients with cirrhosis and 50 healthy controls. Correlations were made to clinical parameters and laboratory data and patients were followed for a median of 22.5 months regarding thrombosis development. H3Cit-DNA was significantly (p < 0.01) elevated in plasma from cirrhosis (66.4 ng/mL) and HCC (63.8 ng/mL) patients compared to healthy controls (31.8 ng/mL). TAT levels showed similar pattern (3.1, 3.7, and 0.0 µg/mL respectively, p < 0.01). MPO-DNA was significantly (p < 0.01) elevated in cirrhosis patients (0.53 O.D.) as compared to controls (0.33 O.D.). Levels of MPO-DNA and H3Cit-DNA correlated positively with Child–Pugh and MELD score. TAT was increased in all Child–Pugh and MELD groups. In multivariable logistic regression, Child B and C liver cirrhosis were independent predictors of elevated H3Cit-DNA in plasma. Levels of MPO-DNA and H3Cit-DNA were similar in patients with or without history of thrombosis, or thrombus formation during follow-up. In conclusion, plasma markers of NET formation are elevated in liver cirrhosis and correlate to the degree of liver dysfunction in patients with liver cirrhosis and/or HCC. The presence of HCC did not further increase the plasma levels of NET markers as compared to patients with cirrhosis only. [ABSTRACT FROM AUTHOR]

This cohort study describes COVID-19–related symptoms persisting 8 months after SARS-CoV-2 infection among Swedish health care workers and self-reported effects of the residual symptoms on respondents' home, work, and social function. [ABSTRACT FROM AUTHOR]

This figure was created with images from BioRender.com. [Display omitted] • Severe COVID-19 is associated with elevated interleukin 6 (IL-6) levels. • Establishing which IL-6 pathway is active enables targeted treatment. • Classical signalling was the dominating IL-6 pathway in severe COVID-19. • Treatment with monoclonal IL-6 receptor antibodies is thus suitable. COVID-19 disease severity and need for intensive care has been associated with profound immune disturbances in which interleukin 6 (IL-6) is central. IL-6 signals through two pathways: classical IL-6 signalling with C-reactive protein (CRP) as a product is pivotal in the acute immune response against pathogens while IL-6 trans -signalling is involved in prolonged inflammation. We measured biomarkers of the IL-6 classical and trans -signalling pathways in patients with moderate or severe COVID-19 in the first wave of the COVID-19 pandemic. In a longitudinal cohort study including patients admitted to Danderyd hospital, Stockholm, Sweden, with COVID-19 (n = 112), plasma IL-6 mirroring activity in both pathways, CRP as marker of classical signalling and the soluble IL-6 receptor (sIL-6R) and soluble glycoprotein 130 (sgp130) as markers of trans -signalling were analysed at baseline. Potential differences in biomarker levels between groups of moderate and severe COVID-19 defined by care level, level of respiratory support and one-month mortality was analysed, as was correlations between biomarkers. In addition, levels 4 months after hospital admission were compared to those at baseline. Levels of IL-6 and CRP were increased in severe COVID-19 whereas IL-6 trans -signalling markers (sIL-6R, sgp130) did not differ between the groups. CRP correlated positively with IL-6 in all patients while correlation with IL-6 could not be demonstrated for sIL-6R and sgp130 in either group. Levels of IL-6, CRP and sIL-6R were significantly decreased after 4 months whereas sgp130 levels increased. Classical signalling is the dominating IL-6 pathway in moderate-severe COVID-19. [ABSTRACT FROM AUTHOR]

Background: Circulating procoagulant extracellular vesicles (EVs) are increased in diseases, such as cancer, sepsis, and COVID-19. EV tissue factor (TF) activity is associated with disseminated intravascular coagulation in sepsis and venous thrombosis in patients with pancreatic cancer and COVID-19. EVs are commonly isolated by centrifugation at ∼20,000 g., Objectives: In this study, we analyzed the TF activity of 2 EV populations enriched for large and small EVs in patients with either sepsis, pancreatic cancer, or COVID-19., Methods: EVs were isolated from plasma by sequential centrifugation at 20,000 g (large EVs, LEVs) and then 100,000 g (small EVs, SEVs). We analyzed EVs from plasma prepared from whole blood samples from healthy individuals with or without lipopolysaccharide (LPS) stimulation as well as EVs from plasma samples from patients with either sepsis, pancreatic cancer, or COVID-19. TF-dependent (EV-TF activity) and TF-independent factor Xa (FXa) generation of the EVs was measured., Results: LPS increased EV-TF activity in LEVs but not SEVs. Similarly, in 2 patients with sepsis who had EV-TF activity above the background of the assay we observed EV-TF activity in LEVs but not SEVs. Patients with pancreatic cancer or COVID-19 had circulating EV-TF activity in both LEVs and SEVs., Conclusion: We recommend that EVs are isolated from plasma from patients by centrifugation at 100,000 g rather than 20,000 g to obtain a more accurate measure of levels of circulating EV-TF activity., (© 2023 The Author(s).)

Heterologous primary immunization against SARS-CoV-2 is part of applied recommendations. However, little is known about duration of immune responses after heterologous vaccine regimens. To evaluate duration of immune responses after primary vaccination with homologous adeno-vectored ChAdOx1 nCoV-19 vaccine (ChAd) or heterologous ChAd/BNT162b2 mRNA vaccine (BNT), anti-spike-IgG and SARS-CoV-2 VOC-neutralizing antibody responses were measured in 354 healthcare workers (HCW) at 2 weeks, 3 months, 5 months and 6 months after the second vaccine dose. T-cell responses were investigated using a whole blood interferon gamma (IFN-γ) release assay 2 weeks and 3 months post second vaccine dose. Two hundred and ten HCW immunized with homologous BNT were enrolled for comparison of antibody responses. In study participants naïve to SARS-CoV-2 prior to vaccination, heterologous ChAd/BNT resulted in 6-fold higher peak anti-spike IgG antibody titers compared to homologous ChAd vaccination. The half-life of antibody titers was 3.1 months (95% CI 2.8-3.6) following homologous ChAd vaccination and 1.9 months (95% CI 1.7-2.1) after heterologous vaccination, reducing the GMT difference between the groups to 3-fold 6 months post vaccination. Peak T-cell responses were stronger in ChAd/BNT vaccinees, but no significant difference was observed 3 months post vaccination. SARS-CoV-2 infection prior to vaccination resulted in substantially higher peak GMTs and IFN-γ levels and enhanced SARS-CoV-2 specific antibody and T cell responses over time. Heterologous primary SARS-CoV-2 immunization with ChAd and BNT elicits a stronger initial immune response compared to homologous vaccination with ChAd. However, although the differences in humoral responses remain over 6 months, the difference in SARS-CoV-2 specific T cell responses are no longer significant three months after vaccination.

Background: Recent reports demonstrate robust serological responses to a single dose of messenger RNA (mRNA) vaccines in individuals previously infected with SARS-CoV-2. Data on immune responses following a single-dose adenovirus-vectored vaccine expressing the SARS-CoV-2 spike protein (ChAdOx1 nCoV-19) in individuals with previous SARS-CoV-2 infection are however limited, and current guidelines recommend a two-dose regimen regardless of preexisting immunity., Methods: We compared RBD-specific IgG and RBD-ACE2 blocking antibodies against SARS-CoV-2 wild type and variants of concern following two doses of the mRNA vaccine BNT162b2 in SARS-CoV-2 naïve healthcare workers (n=65) and a single dose of the adenovector vaccine ChAdOx1 nCoV-19 in 82 healthcare workers more than (n=45) and less than (n=37) 11 months post mild SARS-CoV-2 infection at time of vaccination., Findings: The post-vaccine levels of RBD-specific IgG and neutralizing antibodies against the SARS-CoV-2 wild type and variants of concern including Delta lineage 1.617.2 were similar or higher in participants receiving a single dose of ChAdOx1 nCoV-19 vaccine post SARS-CoV-2 infection (both more than and less than 11 months post infection) compared to SARS-CoV-2 naïve participants who received two doses of BNT162b2 vaccine., Interpretation: Our data support that a single dose ChAdOx1 nCoV-19 vaccine that is administered up to at least 11 months post SARS-CoV-2 infection serves as an effective immune booster. This provides a possible rationale for a single-dose vaccine regimen., Funding: A full list of funding bodies that contributed to this study can be found in the Acknowledgements section., Competing Interests: Declaration of Competing Interest SoH has participated on Astra Zeneca COVID-19 SCG Virtual Advisory Board. Otherwise, the authors declare no competing interests., (Copyright © 2021 The Author(s). Published by Elsevier B.V. All rights reserved.)

Objective: The COVID-19 pandemic poses an immense need for accurate, sensitive and high-throughput clinical tests, and serological assays are needed for both overarching epidemiological studies and evaluating vaccines. Here, we present the development and validation of a high-throughput multiplex bead-based serological assay., Methods: More than 100 representations of SARS-CoV-2 proteins were included for initial evaluation, including antigens produced in bacterial and mammalian hosts as well as synthetic peptides. The five best-performing antigens, three representing the spike glycoprotein and two representing the nucleocapsid protein, were further evaluated for detection of IgG antibodies in samples from 331 COVID-19 patients and convalescents, and in 2090 negative controls sampled before 2020., Results: Three antigens were finally selected, represented by a soluble trimeric form and the S1-domain of the spike glycoprotein as well as by the C-terminal domain of the nucleocapsid. The sensitivity for these three antigens individually was found to be 99.7%, 99.1% and 99.7%, and the specificity was found to be 98.1%, 98.7% and 95.7%. The best assay performance was although achieved when utilising two antigens in combination, enabling a sensitivity of up to 99.7% combined with a specificity of 100%. Requiring any two of the three antigens resulted in a sensitivity of 99.7% and a specificity of 99.4%., Conclusion: These observations demonstrate that a serological test based on a combination of several SARS-CoV-2 antigens enables a highly specific and sensitive multiplex serological COVID-19 assay., Competing Interests: The authors declare no conflict of interest., (© 2021 The Authors. Clinical & Translational Immunology published by John Wiley & Sons Australia, Ltd on behalf of Australian and New Zealand Society for Immunology, Inc.)

Background and Aims: Patients with severe coronavirus disease 2019 (COVID-19) are at significant risk of thrombotic complications. However, their prothrombotic state is incompletely understood. Therefore, we measured in vivo activation markers of hemostasis, plasma levels of hemostatic proteins, and functional assays of coagulation and fibrinolysis in plasma from patients with COVID-19 and determined their association with disease severity and 30-day mortality., Methods: We included 102 patients with COVID-19 receiving various levels of respiratory support admitted to general wards, intermediate units, or intensive care units and collected plasma samples shortly after hospital admission., Results: Patients with COVID-19 with higher respiratory support had increased in vivo activation of coagulation and fibrinolysis, as reflected by higher plasma levels of d-dimer, thrombin-antithrombin, and plasmin-antiplasmin complexes as compared to patients with no to minimal respiratory support and healthy controls. Moreover, the patients with COVID-19 with higher respiratory support exhibited substantial ex vivo thrombin generation and lower ex vivo fibrinolytic capacity, despite higher doses of anticoagulant therapy compared to less severely ill patients. Fibrinogen, factor VIII, and von Willebrand factor levels increased, and ADAMTS13 levels decreased with increasing respiratory support in patients with COVID-19. Low platelet count; low levels of prothrombin, antithrombin, and ADAMTS13; and high levels of von Willebrand factor were associated with short-term mortality., Conclusions: Severe COVID-19 is associated with prothrombotic changes with increased in vivo activation of coagulation and fibrinolysis, despite anticoagulant therapy., Competing Interests: The authors declare no conflict of interest., (© The Authors. 2020 Research and Practice in Thrombosis and Haemostasis published by Wiley Periodicals LLC on behalf of International Society on Thrombosis and Haemostasis.)