SARS-CoV-2 Spike Protein Accumulation in the Skull-Meninges-Brain Axis: Potential Implications for Long-Term Neurological Complications in post-COVID-19 (preprint)

Coronavirus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2), has been associated mainly with a range of neurological symptoms, including brain fog and brain tissue loss, raising concerns about the virus's acute and potential chronic impact on the central nervous system. In this study, we utilized mouse models and human post-mortem tissues to investigate the presence and distribution of the SARS-CoV-2 spike protein in the skull-meninges-brain axis. Our results revealed the accumulation of the spike protein in the skull marrow, brain meninges, and brain parenchyma. The injection of the spike protein alone caused cell death in the brain, highlighting a direct effect on brain tissue. Furthermore, we observed the presence of spike protein in the skull of deceased long after their COVID-19 infection, suggesting that the spike's persistence may contribute to long-term neurological symptoms. The spike protein was associated with neutrophil-related pathways and dysregulation of the proteins involved in the PI3K-AKT as well as complement and coagulation pathway. Overall, our findings suggest that SARS-CoV-2 spike protein trafficking from CNS borders into the brain parenchyma and identified differentially regulated pathways may present insights into mechanisms underlying immediate and long-term consequences of SARS-CoV-2 and present diagnostic and therapeutic opportunities.

Gut microbial disruption in critically ill patients with COVID-19 associated pulmonary aspergillosis (preprint)

Objectives: COVID-19 disease can be exacerbated by Aspergillus superinfection (CAPA). The causes of CAPA are not yet fully understood. Recently, alterations in the gut microbiome have been associated with a complicating course and increasing severity of COVID-19 disease, most likely via immunological mechanisms. Aim of this study was to investigate a potential association between severe CAPA and alterations in the gut and bronchial microbiota. Methods: We performed 16S rRNA gene amplicon sequencing of stool and bronchial samples from a total of 16 COVID-19 patients with CAPA and 26 patients without CAPA. All patients were admitted to the intensive care unit. Results were carefully tested for potential influences on the microbiome during hospitalization. Results: We found that late in COVID-19 disease, CAPA patients exhibited a trend towards reduced gut microbial diversity. Furthermore, late stage CAPA disease showed an increased presence of Staphylococcus epidermidis in the gut. This is not found in late non-CAPA cases or early disease. The analysis of bronchial samples did not show significant results. Conclusions: This is the first study showing alterations in the gut microbiome accompany severe CAPA and possibly influence the hosts immunological response. In particular, an increase of Staphylococcus epidermidis in the intestine could be of importance.

Multidimensional Machine Learning on 2173 COVID-19 Patients in Vietnam (preprint)

INTRODUCTION: The purpose of the study was to determine (a) the overall preclinical character; (b) the cumulative cutoff values and the risk ratio, and (c) the factors associated with severity by a unidimensional and multidimensional analysis on 2173 Sars-Cov2 patients. METHODS: The machine learning study population consisted of 2173 patients (1587 mild and non symptoms patients, 377 moderate patients, 209 severe patients). The status of the patients was recorded from September 2021 to March 2022. RESULTS: The Covid19 Severity directly links with a significant correlation to Age, Score index of the chest X-ray, percentage and quantity of neutrophils, Albumin, C reactive protein, and ratio of Lymphocytes. Their important cut off values (from regression analysis) respectively are: 77.56 years old (the mild-moderate group), 5.53 (the mild-moderate group) and 10.51 (the moderate-severe group), 84.80% (the mild-moderate group) and 87.74%(the moderate-severe group), 11.77G/L (the moderate-severe group), 29.73g/L (the moderate-severe group), 7.46mg/dL (the mild-moderate group), 6.32% (the moderate-severe group). Their significant (p<0.0001) R score correlation with the severity of Covid19, are: 0.44, 0.52 and 0.52, 0.33 and 0.44, 0.42, -0.43, 0.40, -0.41. Their significant risk ratio (p<0.00001) from the meta-analysis, respectively are: 4.19 [3.58-4.95], 3.29 [2.76-3.92] and 3.03 [2.4023;3.8314], 3.18 [2.73-3.70] and 3.32 [2.6480;4.1529], 3.15 [2.6153;3.8025], 3.4[2.91-3.97], 0.46 [0.3650;0.5752] (p<0.00001), 0.34 [0.2743;0.4210]. The pair ALT – Leucocytes and Transferrin – Anion Chloride get the most important correlation shift. ALT – Leucocytes show the important negative link (R=-1, p<0.00001) in the mild group to the significant positive correlation in the moderate group (R=1, p<0.00001). Transferrin–anion Chloride has an important positive association (R=1, p<0.00001) in the mild group with a significant negative correlation in the moderate group (R=-0.59, p<0.00001). The network map and HCA show that in the mild-moderate group, the closest neighbors with the Covid19 severity are ferritins, Age. Then there is C-reactive protein, SI of X-ray, Albumin, and Lactate dehydrogenase, which are the next close neighbors of these three factors. In the moderate-severe group, the closest neighbors with the Covid19 severity are Ferritin, Fibrinogen, Albumin, the quantity of Lymphocytes, SI of X-ray, white blood cells count, Lactate dehydrogenase, and quantity of neutrophils. CONCLUSIONS: Complete multidimensional study in 2173 Covid19 patients in Vietnam shows the whole picture of all the preclinical factors, which may become the clinical reference marker for surveillance and diagnostic management

Improved SARS-CoV-2 neutralization of Delta and Omicron variants of concern after fourth vaccination in hemodialysis patients (preprint)

Background Hemodialysis patients are exposed to a markedly increased risk when infected with SARS-CoV-2. To date it is unclear if hemodialysis patients benefit from a fourth vaccination. Methods A total of 142 hemodialysis patients (median age 72.6 years, 33.8% female) received four COVID-19 vaccinations between December 2020 and March 2022. RDB binding antibody titers were determined in a competitive surrogate neutralization assay. Vero-E6 cells were infected with SARS-CoV-2 variants of concern (VoC) Delta (B.1.617.2) or Omicron (B.1.1.529, sub lineage BA.1) in a biosafety level 3 laboratory to determine serum infection neutralization capacity before and after vaccination. Results After the fourth vaccination serum infection neutralization capacity significantly increased from a 50% inhibitory concentration (IC50, serum dilution factor 1:x) of 247.0 (46.3-1560.8) to 2560.0 (1174.0-2560.0) for the Delta VoC, and from 37.5 (20.0-198.8) to 668.5 (182.2-2560.0) for the Omicron VoC (each p<0.001). A significant increase of the neutralization capacity was even observed for patients who had high antibody titers after three vaccinations (p<0.001). Univariate regression analysis indicated immunosuppressive medication (p=0.001) and hepatitis B vaccination non-response (p=0.046), and multivariate analysis immunosuppressive medication as the only factor associated with a reduced effect against Delta (p<0.001). Ten patients with SARS-CoV-2 breakthrough infection before the fourth vaccination had by trend lower prior neutralization capacity for Omicron (p=0.051). Conclusions Our findings suggest that hemodialysis patients benefit from a fourth vaccination in particular in the light of the highly infectious SARS-CoV-2 Omicron variant. A routinely applied four-time vaccination seems to broaden immunity against variants and would be recommended in hemodialysis patients.

Superior immunity that allows neutralization of all SARS-CoV-2 variants of concern develops in COVID-19 convalescents and naïve individuals after three vaccinations (preprint)

Infection-neutralizing antibody responses after SARS-CoV-2 infection or COVID-19 vaccination are an essential part of antiviral immunity. This immune protection is challenged by the occurrence of SARS-CoV-2 variants of concern (VoCs) with immune escape properties, such as omicron (B.1.1.529) that is rapidly spreading worldwide. Here, we report neutralizing antibody dynamics in a longitudinal cohort of COVID-19 convalescent and naïve individuals vaccinated with mRNA BNT162b2 by quantifying anti-SARS-CoV-2-spike antibodies and determining their avidity and neutralization capacity. A superior infection-neutralizing capacity against all VoCs, including omicron, developed by either two vaccinations of convalescents, or a third vaccination or breakthrough infection of twice-vaccinated naïve individuals. These three consecutive spike antigen exposures resulted in an increasing neutralization capacity per anti-spike antibody unit and were paralleled by stepwise increases in antibody avidity. In conclusion, an infection/vaccination-induced hybrid immunity or a triple immunization induces high-quality antibodies resulting in superior neutralization capacity against VoCs, including omicron.

CMV seropositivity is a potential novel risk factor for severe COVID-19 in non-geriatric patients (preprint)

Background: COVID-19 has so far affected more than 250 million individuals worldwide, causing more than 5 million deaths. Several risk factors for severe disease have been identified, most of which coincide with advanced age. In younger individuals, severe COVID-19 often occurs in the absence of obvious comorbidities. Guided by the finding of cytomegalovirus (CMV)-specific T cells with some cross-reactivity to SARS-CoV-2 in a COVID-19 intensive care unit (ICU) patient, we decided to investigate whether CMV seropositivity is associated with severe or critical COVID-19. Methods: National German COVID-19 bio-sample and data banks were used to retrospectively analyze the CMV serostatus of patients who experienced mild (n=101), moderate (n=130) or severe to critical (n=80) disease by CMV IgG serology. We then investigated the relationship between disease severity and CMV serostatus via statistical models. Results: Non-geriatric patients (< 70 years) with severe COVID-19 were found to have a very high prevalence of CMV-seropositivity, while CMV status distribution in individuals with mild disease was similar to the prevalence in the German population; interestingly, this was not detectable in older patients. Prediction models support the hypothesis that the CMV serostatus might be a strong biomarker in identifying younger individuals with a higher risk of developing severe COVID-19. Conclusions: We identified CMV-seropositivity as a potential novel risk factor for severe COVID-19 in non-geriatric individuals in the studied cohorts. More mechanistic analyses as well as confirmation of similar findings in cohorts representing the currently most relevant SARS-CoV-2 variants should be performed shortly.

Nachhaltige Strategien gegen die COVID-19-Pandemie in Deutschland im Winter 2021/2022 (preprint)

In this position paper, a large group of interdisciplinary experts outlines response strategies against the spread of SARS-CoV-2 in the winter of 2021/2022 in Germany. We review the current state of the COVID-19 pandemic, from incidence and vaccination efficacy to hospital capacity. Building on this situation assessment, we illustrate various possible scenarios for the winter, and detail the mechanisms and effectiveness of the non-pharmaceutical interventions, vaccination, and booster. With this assessment, we want to provide orientation for decision makers about the progress and mitigation of COVID-19.

Gut Bacterial Dysbiosis and Instability is Associated with the Onset of Complications and Mortality in COVID-19 (preprint)

ObjectiveThere is a growing debate about the involvement of the gut microbiome in COVID-19, although it is not conclusively understood whether the microbiome has an impact on COVID-19, or vice versa, especially as analysis of amplicon data in hospitalized patients requires sophisticated cohort recruitment and integration of clinical parameters. Here, we analyzed fecal and saliva samples from SARS-CoV-2 infected and post COVID-19 patients and controls considering multiple influencing factors during hospitalization. Design16S rRNA gene sequencing was performed on fecal and saliva samples from 108 COVID-19 and 22 post COVID-19 patients, 20 pneumonia controls and 26 asymptomatic controls. Patients were recruited over the first and second corona wave in Germany and detailed clinical parameters were considered. Serial samples per individual allowed intra-individual analysis. ResultsWe found the gut and oral microbiota to be altered depending on number and type of COVID-19-associated complications and disease severity. The occurrence of individual complications was correlated with low-risk (e.g., Faecalibacterium prausznitzii) and high-risk bacteria (e.g., Parabacteroides). We demonstrated that a stable gut bacterial composition was associated with a favorable disease progression. Based on gut microbial profiles, we identified a model to estimate mortality in COVID-19. ConclusionGut microbiota are associated with the occurrence of complications in COVID-19 and may thereby influencing disease severity. A stable gut microbial composition may contribute to a favorable disease progression and using bacterial signatures to estimate mortality could contribute to diagnostic approaches. Importantly, we highlight challenges in the analysis of microbial data in the context of hospitalization.

Early Reduction of SARS-CoV-2 Replication in Bronchial Epithelium by Kinin B2 Receptor Antagonism (preprint)

ABSTRACT Background SARS-CoV2 has evolved to enter the host via the ACE2 receptor which is part of the Kinin-kallirein pathway. This complex pathway is only poorly understood in context of immune regulation but critical to control infection. This study examines SARS-CoV2 infection and epithelial mechanisms of the kinin-kallikrein system at the kinin B 2 receptor level in SARS-CoV-2 infection that is of direct translational relevance. Methods From acute SARS-CoV-2-positive patients and -negative controls, transcriptomes of nasal brushings were analyzed. Primary airway epithelial cells (NHBEs) were infected with SARS-CoV-2 and treated with the approved B 2 R antagonist icatibant. SARS-CoV-2 RNA RT-qPCR, cytotoxicity assays, plaque assays and transcriptome analyses were performed. The treatment effect was further studied in a murine airway inflammation model in vivo . Results Here, we report a broad and strong upregulation of kallikreins and the kinin B 2 receptor (B 2 R) in the nasal mucosa of acutely symptomatic SARS-CoV-2-positive patients. A B 2 R antagonist impeded SARS-CoV-2 replication and spread in NHBEs, as determined in plaque assays on Vero E6 cells. B 2 R antagonism reduced the expression of SARS-CoV-2 entry receptor ACE2 in vitro and in a murine airway inflammation model in vivo . In addition, it suppressed gene expression broadly, particularly genes involved in G-protein-coupled-receptor signaling and ion transport. Conclusions In summary, this study provides evidence that treatment with B 2 R antagonists protects airway epithelial cells from SARS-CoV-2 by inhibiting its replication and spread, through the reduction of ACE2 levels and the interference with several cellular signaling processes. Future clinical studies need to shed light on the airway protection potential of approved B 2 R antagonists, like icatibant, in the treatment of early-stage COVID-19.

New susceptibility loci for severe COVID-19 by detailed GWAS analysis in European populations (preprint)

Due to the highly variable clinical phenotype of Coronavirus disease 2019 (COVID-19), deepening the host genetic contribution to severe COVID-19 may further improve our understanding about underlying disease mechanisms. Here, we describe an extended GWAS meta-analysis of 3,260 COVID-19 patients with respiratory failure and 12,483 population controls from Italy, Spain, Norway and Germany, as well as hypothesis-driven targeted analysis of the human leukocyte antigen (HLA) region and chromosome Y haplotypes. We include detailed stratified analyses based on age, sex and disease severity. In addition to already established risk loci, our data identify and replicate two genome-wide significant loci at 17q21.31 and 19q13.33 associated with severe COVID-19 with respiratory failure. These associations implicate a highly pleiotropic ~0.9-Mb 17q21.31 inversion polymorphism, which affects lung function and immune and blood cell counts, and the NAPSA gene, involved in lung surfactant protein production, in COVID-19 pathogenesis.

Recruitment of highly functional SARS-CoV-2-specific CD8+ T cell receptors mediating cytotoxicity of virus-infected target cells in non-severe COVID-19 (preprint)

ABSTRACT T cell immunity is crucial for the control of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections and has been widely characterized on a quantitative level. In contrast, the quality of such T cell responses has been poorly investigated, in particular in the case of CD8 + T cells. Here, we explored the quality of SARS-CoV-2-specific CD8 + T cell responses in individuals who recovered from mild symptomatic infections, through which protective immunity should develop, by functional characterization of their T cell receptor (TCR) repertoire. CD8 + T cell responses specific for SARS-CoV-2-derived epitopes were low in frequency but could be detected robustly early as well as late - up to twelve months - after infection. A pool of immunodominant epitopes, which accurately identified previous SARS-CoV-2 infections, was used to isolate TCRs specific for epitopes restricted by common HLA class I molecules. TCR-engineered T cells showed heterogeneous functional avidity and cytotoxicity towards virus-infected target cells. High TCR functionality correlated with gene signatures of T cell function and activation that, remarkably, could be retrieved for each epitope:HLA combination and patient analyzed. Overall, our data demonstrate that highly functional HLA class I TCRs are recruited and maintained upon mild SARS-CoV-2 infection. Such validated epitopes and TCRs could become valuable tools for the development of diagnostic tests determining the quality of SARS-CoV-2-specific CD8 + T cell immunity, and thereby investigating correlates of protection, as well as to restore functional immunity through therapeutic transfer of TCR-engineered T cells.

Heterologous prime-boost vaccination with ChAdOx1 nCoV-19 and BNT162b2 mRNA (preprint)

Administration of a first dose of the COVID-19 vaccine ChAdOx1 nCoV-19 (Vaxzevria(R), AstraZeneca) is associated with a certain risk for vaccine-induced immune thrombotic thrombocytopenia. Therefore, several countries have recommended replacing the second dose of ChAdOx1 nCoV-19 with an mRNA-based vaccine as a precautionary measure, although data on safety and efficacy of such heterologous prime-boost regimen are sparse. Therefore, vaccinees, who had received a heterologous vaccination using ChAdOx1 nCoV-19 as prime and BNT162b2 (Comirnaty(R), BioNTech-Pfizer) mRNA as boost vaccination were offered SARS-CoV-2 antibody testing to quantify their vaccine-induced neutralizing antibody response. The results were compared to cohorts of healthcare workers or volunteers, who received homologous BNT162b2 or homologous ChAdOx1 nCoV-19 vaccination regimens, respectively. A striking increase of vaccine-induced SARS-CoV-2 neutralizing antibody activity was observed in 229 vaccinees that received a BNT162b2 boost 9 to 12 weeks after ChAdOx1 nCoV-19 prime. In our cohort comprising over 480 individuals, the heterologous vaccination scheme induced significantly higher neutralizing antibody titers than homologous ChAdOx1 nCoV-19 and even than homologous BNT162b2 vaccination. This proves that a single dose of a COVID-19 mRNA vaccine after ChAdOx1 nCoV-19 prime vaccination is sufficient to achieve high neutralizing antibody levels predicting immune protection from SARS-CoV-2 infection, and may even increase vaccine efficacy offering an alternative in a setting of vaccine shortage.

Long-term follow-up of SARS-CoV-2 convalescents reveals distinct magnitude of spike-specific immunity after viral re-exposure and vaccination (preprint)

Infection with the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) is controlled by the host´s immune response1-4, but longitudinal follow-up studies of virus-specific immunity to evaluate protection from re-infection are lacking. Here, we report the results from a prospective study that started during the first wave of the COVID-19 pandemic in spring 2020, where we identified 91 convalescents from mild SARS-CoV-2 infection among 4554 health care workers. We followed the dynamics and magnitude of spike-specific immunity in convalescents during the spontaneous course over ≥ 9 months, after SARS-CoV-2 re-exposure and after BNT162b2 mRNA vaccination. Virus-neutralizing antibodies and spike-specific T cell responses with predominance of IL-2-secreting polyfunctional CD4 T cells continuously declined over 9 months, but remained detectable at low levels. After a single vaccination, convalescents simultaneously mounted strong antibody and T cell responses against the SARS-CoV-2 spike proteins. In naïve individuals, a prime vaccination induced preferentially IL-2-secreting CD4 T cells that preceded production of spike-specific virus-neutralizing antibodies after boost vaccination. Response to vaccination, however, was not homogenous. Compared to four individuals among 455 naïve vaccinees (0.9%), we identified 5/82 (6.1%) convalescents with a delayed response to vaccination. These convalescents had originally developed dysfunctional spike-specific immune responses after SARS-CoV-2 infection, and required prime and boost vaccination to develop strong spike-specific immunity. Importantly, during the second wave of the COVID-19 pandemic in fall/winter of 2021 and prior to vaccination we detected a surge of virus-neutralizing antibodies consistent with re-exposure to SARS-CoV-2 in 6 out of 82 convalescents. The selective increase in virus-neutralizing antibodies occurred without systemic re-activation of spike-specific T cell immunity, whereas a single BNT162b2 mRNA vaccination sufficed to induce strong spike-specific antibody and systemic T cell responses in the same individuals. These results support the notion that BNT162b2 mRNA vaccination synchronizes spike-specific immunity in all convalescents of mild SARS-CoV-2 infection and may provide additional protection from re-infection by inducing more rigorous stimulation of spike-specific T cell immunity than re-exposure with SARS-CoV-2.

Picomolar inhibition of SARS-CoV-2 variants of concern by an engineered ACE2-IgG4-Fc fusion protein (preprint)

SARS-CoV-2 enters host cells after binding through its spike glycoprotein to the angiotensin-converting enzyme 2 (ACE2) receptor. Soluble ACE2 ectodomains bind and neutralize the virus, yet their short in vivo half-live limits their therapeutic use. This limitation can be overcome by fusing the fragment crystallizable (Fc) part of human immunoglobulin G (IgG) to the ACE2 ectodomain, but this bears the risk of unwanted Fc-receptor activation and antibody-dependent disease enhancement. Here, we describe optimized ACE2-IgG4-Fc fusion constructs that avoid Fc-receptor activation, preserve the desired ACE-2 enzymatic activity and show promising pharmaceutical properties. The engineered ACE2-IgG4-Fc fusion proteins neutralize the original SARS-CoV, pandemic SARS-CoV-2 as well as the rapidly spreading SARS-CoV-2 variants-of-concern, B.1.17 and B.1.351. Importantly, these variants-of-concern are inhibited at picomolar concentrations proving that ACE-2-IgG4 maintains – in contrast to therapeutic antibodies - its full antiviral potential. Thus, ACE2-IgG4-Fc fusion proteins are promising candidate anti-antivirals to combat the current and future pandemics.

The new generation hDHODH inhibitor MEDS433 hinders the in vitro replication of SARS-CoV-2 (preprint)

Identification and development of effective drugs active against SARS-CoV-2 are urgently needed. Here, we report on the anti-SARS-CoV-2 activity of MEDS433, a novel inhibitor of human dihydroorotate dehydrogenase (hDHODH), a key cellular enzyme of the de novo pyrimidines biosynthesis. MEDS433 inhibits in vitro virus replication in the low nanomolar range, and through a mechanism that stems from its ability to block hDHODH activity. MEDS433 thus represents an attractive candidate to develop novel anti-SARS-CoV-2 agents.

Efficient inhibition of SARS-CoV-2 strains by a novel ACE2-IgG4-Fc fusion protein with a stabilized hinge region (preprint)

The novel severe acute respiratory syndrome (SARS)-like coronavirus (SARS-CoV-2) enters its host cells after binding to the angiotensin-converting enzyme 2 (ACE2) via its spike glycoprotein. This interaction is critical for virus entry and virus-host membrane fusion. Soluble ACE2 ectodomains bind and neutralize the virus but the short in vivo half-lives of soluble ACE2 limits its therapeutic use. Fusion of the fragment crystallizable (Fc) part of human immunoglobulin G (IgG) to the ACE2 ectodomain can prolong the in vivo half-life but bears the risk of unwanted Fc-receptor activation and antibody-dependent disease enhancement. Here, we describe optimized ACE2-Fc fusion constructs that avoid Fc-receptor binding by using IgG4-Fc as a fusion partner. The engineered ACE2-IgG4-Fc fusion proteins described herein exhibit promising pharmaceutical properties and a broad antiviral activity at single-digit nanomolar concentration. In addition, they allow to maintain the beneficial enzymatic activity of ACE2 and thus are very promising candidate antivirals broadly acting against coronaviruses.

Strategies for Infection Control and Prevalence of Anti-SARS-CoV-2 IgG Antibodies in 4,554 Employees of a University Hospital in Munich, Germany (preprint)

Background: Hospital staff are at high risk of infection during the coronavirus disease (COVID-19) pandemic. We analysed the exposure characteristics, efficacy of protective measures, and transmission dynamics in this hospital-wide prospective seroprevalence study.Methods: Overall, 4554 individuals were tested for anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) IgG antibodies using a chemiluminescent immunoassay. Individual risk factors, use of personal protective equipment (PPE), occupational exposure, previous SARS-CoV-2 infection, and symptoms were assessed using a questionnaire and correlated to anti-SARS-CoV-2 IgG antibody titres and PCR testing results. Odds ratios with corresponding exact 95% confidence intervals were used to evaluate associations between individual factors and seropositivity. Spatio-temporal trajectories of SARS-CoV-2-infected patients and staff mobility within the hospital were visualised to identify local hotspots of virus transmission.Findings: The overall seroprevalence of anti-SARS-CoV-2-IgG antibody was 2•4% [95% CI 1•9–2•9]. Patient-facing staff, including those working in COVID-19 areas, had a similar probability of being seropositive as non-patient-facing staff. Prior interaction with SARS-CoV-2-infected co-workers or private contacts and unprotected exposure to COVID-19 patients increased the probability of seropositivity. Loss of smell and taste had the highest positive predictive value for seropositivity. The rate of asymptomatic SARS-CoV-2 infections was 25•9%, and higher anti-SARS-CoV-2 IgG antibody titres were observed in symptomatic individuals. Spatio-temporal hotspots of SARS-CoV-2-positive staff and patients only showed partial overlap.Interpretation: Patient-facing work in a healthcare facility during the SARS-CoV-2 pandemic may be safe if adequate PPE and hygiene measures are applied. The high numbers of asymptomatic SARS-CoV-2 infections that escaped detection by symptomatic testing underline the value of cross-sectional seroprevalence studies. Unprotected contact is a major risk factor for infection and argues for the rigorous implementation of hygiene measures. Funding: The study was funded by the Board of Directors of the University Hospital rechts der Isar, Munich.Declaration of Interests: The authors declare no competing interests.Ethics Approval Statement: The study was approved by the Ethics Committee of the Technical University of Munich, School of Medicine (approval number: 216/20S).

Strategies for infection control and prevalence of anti-SARS-CoV-2 IgG in 4,554 employees of a university hospital in Munich, Germany (preprint)

Background Hospital staff are at high risk of infection during the coronavirus disease (COVID-19) pandemic. We analysed the exposure characteristics, efficacy of protective measures, and transmission dynamics in this hospital-wide prospective seroprevalence study. Methods and Findings Overall, 4554 individuals were tested for anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) IgG antibodies using a chemiluminescent immunoassay. Individual risk factors, use of personal protective equipment (PPE), occupational exposure, previous SARS-CoV-2 infection, and symptoms were assessed using a questionnaire and correlated to anti-SARS-CoV-2 IgG antibody titres and PCR testing results. Odds ratios with corresponding exact 95% confidence intervals were used to evaluate associations between individual factors and seropositivity. Spatio-temporal trajectories of SARS-CoV-2-infected patients and staff mobility within the hospital were visualised to identify local hotspots of virus transmission. The overall seroprevalence of anti-SARS-CoV-2-IgG antibody was 2.4% [95% CI 1.9-2.9]. Patient-facing staff, including those working in COVID-19 areas, had a similar probability of being seropositive as non-patient-facing staff. Prior interaction with SARS-CoV-2-infected co-workers or private contacts and unprotected exposure to COVID-19 patients increased the probability of seropositivity. Loss of smell and taste had the highest positive predictive value for seropositivity. The rate of asymptomatic SARS-CoV-2 infections was 25.9%, and higher anti-SARS-CoV-2 IgG antibody titres were observed in symptomatic individuals. Spatio-temporal hotspots of SARS-CoV-2-positive staff and patients only showed partial overlap. Conclusions Patient-facing work in a healthcare facility during the SARS-CoV-2 pandemic may be safe if adequate PPE and hygiene measures are applied. The high numbers of asymptomatic SARS-CoV-2 infections that escaped detection by symptomatic testing underline the value of cross-sectional seroprevalence studies. Unprotected contact is a major risk factor for infection and argues for the rigorous implementation of hygiene measures.