Search Results (564)

Urine-based immunoassay is a non-invasive method with demonstrated utility in detecting anti-SARS-CoV-2 antibodies in unvaccinated patients with COVID-19. To evaluate urine’s potential for serological surveys in a real-world setting, SARS-CoV-2 serology was performed on urine samples from vaccinated individuals, both with and without prior confirmed COVID-19. (1) Methods: An in-house indirect ELISA was used to measure antibodies against recombinant spike (S) and nucleocapsid (N) proteins of SARS-CoV-2 in urine and paired serum from 149 individuals vaccinated with Janssen AD26.COV2.S, an S protein-based COVID-19 vaccine. (2) Results: Anti-S and anti-N levels were higher in the urine and serum of participants with confirmed prior COVID-19 compared to those without prior infection. Urinary anti-S effectively distinguished vaccinated individuals with (AUC = 0.96) and without (AUC = 0.88) prior infection from negative controls (non-vaccinated, non-previously infected individuals) (p < 0.0001). Among vaccinated participants, urinary anti-S and anti-N identified prior infection, with AUC values of 0.73 (p < 0.0001) and 0.60 (p = 0.03), respectively, being recorded. (3) Conclusions: Findings indicate that urinary anti-SARS-CoV-2 antibodies reflect AD26.COV2.S vaccination and previous COVID-19. To further advance the methodology, studies with larger sample sizes and a greater diversity of COVID-19 vaccines are required. Full article

Solid organ transplant recipients (SOTRs) are at high risk of severe coronavirus disease 2019 (COVID-19), therefore early treatment of mild infections is crucial to prevent increased morbidity and mortality. The effectiveness of early treatment in SOTRs has yet to be fully characterized due to the emergence of new SARS-CoV-2 variants and to COVID-19 vaccination implementation. The aim of this single-center retrospective study is to evaluate the outcomes, safety and impact on SARS-CoV-2 viral load kinetics of COVID-19 early treatment in SOTRs. The study includes 80 SOTRs with a laboratory-confirmed diagnosis of symptomatic SARS-CoV-2 infection enrolled between January and October 2022 and treated with either monoclonal antibodies or antivirals. All patients received COVID-19 vaccination and 68.8% of them showed detectable levels of anti-spike (S) antibodies. The occurrence of clinical events (hospitalization, intensive care unit admission, or death) was assessed within 30 days after treatment initiation. The quantification of SARS-CoV-2 viral load were performed at baseline and at day-7. The rate of hospitalization was 2.5% [0.3–9%] and no deaths occurred. All patients completed treatment with no serious adverse events. Median viral load decrease was 0.48 [0.26–0.69] log₂ cycle threshold (ct) values, with no significant differences between SOTRs treated with monoclonal antibodies and those treated with antivirals. Viral load decrease was significantly associated with positive anti-s serology at baseline ($\beta$ = 0.196, p = 0.01), number of days between symptom onset and treatment ($\beta$ = 0.05, p = 0.03) and the number of comorbidities ($\beta$ = −0.05, p = 0.03). We provide evidence of real-world effectiveness of early therapy in SOTRs infected with SARS-CoV-2 and demonstrate the relevant role of humoral response to vaccination in enhancing early viral load decay during treatment. Full article

Background: COVID-19 vaccination has been a key tool in protecting healthcare workers (HCWs), but breakthrough infections have occurred. The durability of vaccine-induced immunity and its impact on HCWs remain critical for public health strategies. Methods: In this small cohort study (n = 32), we assessed antibody levels and breakthrough infection rates in HCWs over 12 months post-vaccination, providing insights for booster strategies and infection control. A cohort of 32 HCWs was screened for SARS-CoV-2 infection using weekly self-administered swabs and blood samples collected at baseline, 6 months, and 12 months. SARS-CoV-2 antibodies (IgG, IgM) targeting spike proteins and nucleocapsids were analyzed using a multi-antigen serology panel. Pooled nucleic acid testing was employed for infection detection. Results: Nine participants showed breakthrough infections, with nucleocapsid antibodies indicating prior infection. Eight of these cases occurred after the third vaccine dose during the Omicron-dominant period. Anti-spike antibody levels declined significantly in participants without prior infection, while those with breakthrough infections exhibited increased levels. The half-life of S1 and S1 receptor-binding domain (RDB) vaccine-induced antibodies was 144 and 166 days, respectively, which aligns with CDC data. These findings provide valuable insights for determining the optimal timing of booster doses. Conclusions: Our findings highlight the waning antibody levels over time and the occurrence of breakthrough infections. Although based on a small sample, these data support the need for ongoing monitoring and timely boosters. Full article

Background: This study aimed to assess the prevalence of SARS-CoV-2 infection, vaccination, and immune status among a population, both Dentists and University Professors, within a clinical setting at one and at 12 months after COVID-19 vaccination. Methods: A cross-sectional study involving 47 professionals (aged 27–52) was conducted in the University Fernando Pessoa. Participants completed an online survey on SARS-CoV-2 infection status and vaccination, received and provided plasma samples for serological analysis. The protocol was approved by the UFP-Ethics Committee. Anti-S1-RBD SARS-CoV-2 IgM and IgG antibody titration values (AU/mL) were measured, by enzyme-linked-immunosorbent assay (ELISA), with reactive immunoglobulins (Ig) seropositivity for values ≥1 AU/mL. Results: SARS-CoV-2 infection rate increased from 8.5% in July 2021 to 48.9% in June 2022, with 8.5% experiencing reinfection. Vaccination rate was 91.5% by July 2021 and increased slightly to 93.6% by June 2022; 72.3% of the sample received a third dose. IgG seropositivity increased from 91.5% to 95.7% in June 2022. After one-year, significant associations were found between IgG seropositivity and both participant’s age (p = 0.009; <50 years) and vaccine doses (p = 0.003; 1–3 doses) received. Conclusions: SARS-CoV-2 infection rate, vaccination, and IgG seropositivity rates were high and increased over one year. The age and vaccination status were associated with the immunity status at 12th month follow-up. Findings highlight variability in IgG seroprevalence due to multiple influencing factors, which justifies future studies. Full article

Background: Vaccination effectively reduces the risk of infection, including COVID-19 yet older adults often receive insufficient attention despite their increased vulnerability. The study aimed to correlate serological results with underlying conditions, vaccination status, and COVID-19 history. Methods: This non-interventional, multicenter study aimed to assess vaccination coverage and SARS-CoV-2 antibody levels among residents of eight long-term care facilities (LTCFs) in Southern Poland. Data collection took place between January and June 2022, with 429 participants recruited based on their ability to provide informed consent and their residency in LTCFs. Sociodemographic data, medical history, and COVID-19-related information—including infection history and vaccination status—were collected through surveys. Blood samples were obtained for serological testing using enzyme-linked immunosorbent assays (ELISA) to detect anti-SARS-CoV-2 antibodies. Statistical analysis, including Spearman’s correlation, revealed significant associations between antibody levels and vaccination status, as well as between RT-PCR-confirmed COVID-19 infections and higher antibody titers. Results: Among the seven different qualitative serological, only the Anti-SARS-CoV-2 NCP (IgG) and Anti-SARS-CoV-2 (IgA) tests showed a positive correlation with the Anti-SARS-CoV-2 QuantiVac (IgG) test, which was used as a comparator. A weak correlation was noted with the age of the residents. Conclusions: Our findings suggest that vaccination positively influences antibody responses, underscoring the importance of immunization among LTCF residents. Additionally, certain comorbidities—such as degenerative joint disease and diabetes—showed weak correlations with higher antibody levels. This study provides valuable insights into the humoral immune response to COVID-19 in vulnerable populations residing in LTCFs. Full article

Background: The longitudinal RisCoin study investigated risk factors for COVID-19 vaccination failure among healthcare workers (HCWs) and patients with inflammatory bowel disease (IBD) at a University Hospital in Germany. Since the hospital served as the study sponsor and employer of the HCW, we implemented a custom mobile application. We aimed to evaluate the implementation, adherence, benefits, and limitations of this study’s app. Methods: The app allowed secure data collection through questionnaires, disseminated serological results, and managed bidirectional communication. Access was double-pseudonymized and irreversibly anonymized six months after enrollment. Download frequency, login events, and questionnaire submissions between October 2021 and December 2022 were analyzed. Multivariable logistic regression identified factors associated with app adherence. Results: Of the 3979 participants with app access, 3622 (91%) used the app; out of these, 1016 (28%) were “adherent users” (≥12 submitted questionnaires). App adherence significantly increased with age. Among HCW, adherent users were more likely to be non-smokers (p < 0.001), working as administrators or nursing staff vs. physicians (p < 0.001), vaccinated against influenza (p < 0.001), and had not travelled abroad in the past year (p < 0.001). IBD patients exposed to SARS-CoV-2 (p = 0.0133) and those with adverse events following the second COVID-19 vaccination (p = 0.0171) were more likely adherent app users. Despite technical issues causing dropout or non-adherence, the app served as a secure solution for cohort management and longitudinal data collection. Discussion: App-based cohort management enabled continuous data acquisition and individualized care while providing flexibility and anonymity for the study team and participants. App usability, technical issues, and cohort characteristics need to be thoroughly considered prior to implementation to optimize usage and adherence in clinical research. Full article

Background: Hemodialysis patients, due to impaired kidney function and compromised immune responses, face increased risks from SARS-CoV-2. Anti-nucleocapsid IgG (anti-IgG N) antibodies are a commonly used marker to assess prior infection in the general population; however, their efficacy for hemodialysis patients remains unclear. Methods: A retrospective study of 361 hemodialysis patients evaluated anti-IgG N antibodies for detecting prior SARS-CoV-2 infection. Antibody levels were measured using a chemiluminescence immunoassay (CLIA) over the four time points. Boxplots illustrated antibody distribution across sampling stages and infection status. Logistic regression and receiver operating characteristic (ROC) curve analysis determined diagnostic accuracy, sensitivity, specificity, and optimal cutoff values. Results: Among the 361 hemodialysis patients, 36 (10.0%) had SARS-CoV-2 infection. Sex distribution showed a trend toward significance (p = 0.05). Boxplot analysis showed that anti-IgG N levels remained low in non-infected patients but increased in infected patients, peaking at the third sampling. Anti-IgG N demonstrated high diagnostic accuracy (AUC: 0.973–0.865) but declined over time (p = 0.00525). The optimal cutoff at C1 was 0.01 AU/mL (sensitivity 1.00, specificity 0.94). Adjusted models had lower predictive value. Conclusions: Anti-IgG N antibodies showed high diagnostic accuracy for detecting prior SARS-CoV-2 infection in hemodialysis patients, though performance declined over time. These findings highlight the need for tailored diagnostic strategies in this vulnerable population. Full article

(1) Background: The ongoing global health threat posed by SARS-CoV-2 requires reliable and accessible diagnostic tools, especially in resource-limited settings where RT-qPCR may be impractical. This study describes the development and validation of two enzyme-linked immunosorbent assays (ELISA) designed to detect anti-SARS-CoV-2 IgG antibodies employing recombinant S1 and S2 spike protein subunits. (2) Methods: The assays were optimized and validated using serum samples from 354 RT-qPCR-confirmed hospitalized patients and 337 pre-pandemic blood donors. (3) Results: The S1-based ELISA achieved a 52.8% sensitivity and a specificity of 93.5%, with an area under the ROC curve (AUC) of 71.6%. In contrast, the S2-based ELISA demonstrated superior diagnostic performance, with a sensitivity of 63.7%, a specificity of 99.7%, and an AUC of 83.1%. Cross-reactivity analysis using sera from individuals with unrelated infectious diseases confirmed the high specificity of the S2-ELISA. Time-stratified analysis revealed that sensitivity increased with time, peaking between 15 and 21 days post-symptom onset. Compared to commercial serological assays, the S2-ELISA demonstrated comparable or improved performance, particularly in specificity and diagnostic odds ratio. (4) Conclusions: The S2-ELISA offers a robust, highly specific, and operationally simple tool for serological detection of SARS-CoV-2 infection. Its strong diagnostic performance and accessibility make it well-suited for implementation in diverse epidemiological settings, particularly where molecular testing is limited. The development of affordable, validated serological assays such as this is critical for strengthening surveillance, understanding transmission dynamics, and informing public health responses. Full article

The COVID-19 pandemic highlighted the need for rapid, cost-effective tools to monitor transmission and immune response. We developed two novel paper-based colorimetric biosensors using glutaraldehyde as a protein dye—its first use in this context. Glutaraldehyde reacts with amino groups to generate a brown color, enabling detection of SARS-CoV-2 antibodies. Wathman filter paper was functionalized with (3-aminopropyl)triethoxysilane (APTES) to immobilize virus-like particles (VLPs) and nucleocapsid protein (N-protein) as biorecognition elements. Upon incubation with antibody-containing samples, glutaraldehyde enabled colorimetric detection using RGB analysis in ImageJ software. Both sensors showed a linear correlation between antibody concentration and RGB values in buffer and serum. The VLP sensor responded linearly within the range of 1.0–20 µg/mL (green coordinate) in 500-fold diluted serum and the N-protein sensor from 1.0–40 µg/mL (blue coordinate) in 250-fold diluted serum. Both sensors demonstrated good selectivity, with glucose causing up to 18% interference. These biosensors represent a paradigm shift, as they provide a sensitive, user-friendly, and cost-effective option for semi-quantitative serological analysis. Furthermore, their versatility goes beyond the detection of SARS-CoV-2 antibodies and suggests broader applicability for various molecular targets. Full article

Post-COVID-19 syndrome (PCS) is a common outcome of severe COVID-19 infection; however, less is known about PCS following mild COVID-19. Healthcare workers (HCWs) are more susceptible to acquiring COVID-19 and potentially suffering physical and psychological morbidity secondary to their role. We surveyed HCWs at four hospitals in northeast England at two timepoints during the pandemic, assessing physical and psychophysiological symptoms of PCS, alongside associated factors, whilst also testing for COVID-19 status by SARS-CoV-2 serology and reviewing evidence of infection from previous PCR nasopharyngeal swabs. Of the 379 participants at baseline and 250 HCWs recruited 18 months later, 46% and 64% (respectively) had evidence of previous COVID-19, with no significant associations between COVID-19 status or demographics and symptom scores or self-described PCS. Depression and fatigue were more common later in the pandemic. Furthermore, 20% self-described having PCS, 34% of whom had no evidence of previous COVID-19. Scores for fatigue, pain, mobility, anxiety, and depression were significantly worse in the PCS group compared to those without ongoing symptoms. Significant proportions of HCWs continued to suffer debilitating symptoms during the later pandemic period, although a significant minority had no evidence of previous COVID-19 infection, suggesting that other factors may be involved in their symptomatology. Full article

Community-based serosurveillance for emerging zoonotic viruses can provide a powerful and cost-effective measurement of cryptic spillovers. Betacoronaviruses, including SARS-CoV, SARS-CoV-2 and MERS-CoV, are known to infect bats and can cause severe respiratory illness in humans, yet remain under-surveyed in high-risk populations. This study aimed to determine the seroprevalence of betacoronaviruses in an occupational cohort in contact with bats before and after the emergence of SARS-CoV-2. Serum samples from pre- and post-COVID-19 pandemic were screened using antigen-based multiplex microsphere immunoassays (MMIAs) and a multiplex surrogate virus neutralization test (sVNT). Pre-pandemic samples showed no SARS-CoV-2 antibodies, while post-pandemic samples from vaccinated participants displayed binding and neutralizing antibodies against SARS-CoV-2 and a related bat CoV. Furthermore, one participant (1/237, 0.43%) had persistent antibodies against MERS-CoV in 2017, 2018 and 2021 but was seronegative in 2023, despite reporting no history of traveling abroad or severe pneumonia. The observed sustained antibody levels indicate a possible exposure to MERS-CoV or a MERS-CoV-like virus, although the etiology and clinical relevance of this finding remains unclear. Ongoing surveillance in high-risk populations remains crucial for understanding virus epidemiology and mitigating zoonotic transmission risk. Full article

Congenital Rubella Syndrome (CRS) results from maternal infection with the rubella virus during pregnancy, particularly in the first trimester, when the risk of vertical transmission and severe fetal damage is highest. CRS is characterized by a broad spectrum of congenital anomalies, including sensorineural hearing loss, congenital heart defects, cataracts, neurodevelopmental delay, and behavioral disorders. Despite the absence of specific antiviral therapies, active immunization remains the only effective strategy to prevent rubella infection and its congenital consequences. Global immunization efforts, particularly in the Americas, have led to the elimination of rubella and CRS in several countries. However, challenges persist in the post-elimination era, including declining vaccine coverage, vaccine hesitancy, and setbacks caused by the COVID-19 pandemic. Diagnosis relies on maternal serology, fetal imaging, postnatal antibody testing, and molecular techniques. Management requires long-term, multidisciplinary follow-up due to the complex and lifelong sequelae affecting sensory, motor, and cognitive development. This review highlights the clinical, epidemiological, and pathophysiological aspects of CRS, while emphasizing the urgent need to maintain high vaccination coverage and strengthen surveillance systems. Sustained public health commitment is essential to prevent the reemergence of rubella and protect future generations from this preventable syndrome. Full article

Public safety personnel (PSP) are known to experience difficult and demanding occupational environments, which were further complicated by the COVID-19 crisis. While public safety research typically focuses on the impact of operational stressors on PSP functioning and wellbeing, relatively less is known about the types and impacts of organizational stressors and how all these affect social wellbeing during the pandemic. The current study surveyed Canadian firefighters (n = 123), paramedics (n = 246), and public safety communicators (n = 48) that continued to serve the public over the course of the pandemic. Participants responded to two open-ended survey questions about how COVID-19 affected their lives at work and home. Using an inductive thematic analysis approach, responses were coded to identify emergent, data-driven themes while drawing on existing theory for analysis. Across occupational groups, qualitative analyses revealed that the public safety measures imposed by the COVID-19 pandemic further exacerbated existing operational and organizational strains, including increased exposure to distressing calls, absenteeism and coping with alcohol, and a lack of support from management. Participants also identified financial strain and housing insecurity as stressors, as well as frustration and helplessness at others’ non-compliance with public health advisories and protocols. Communication surrounding the rationale behind government decision-making, the efficacy of serology tests, and rates of infection were also identified. Together, these findings offer a nuanced understanding of the interplay among operational, organizational, and social stressors experienced by Canadian PSP during the COVID-19 pandemic, illuminating their impact on mental health and wellbeing, and identifying targeted areas of focus for future planning and meaningful intervention to support PSP wellness. Full article

Background: Frequency indicators are used by epidemiologists to facilitate public health professionals in estimating the impact of diseases. As of April 2022, Romania had reported 2.8 million confirmed COVID-19 cases to the World Health Organization, equating to a prevalence rate of 13.94%. A more accurate method for assessing the cumulative number of cases is the use of seroprevalence studies. This study retrospectively evaluates infection trends in Romania to enhance understanding of the virus’s spread and may support future comparative analyses of public health responses and community-level immunity. Methods: We analyzed 51,533 qualitative test results for high-affinity IgG antibodies targeting the SARS-CoV-2 nucleocapsid protein. Results: The largest proportion of tested individuals (59.4%) was aged 18–49 years. Among all serological tests, 18,980 were positive, corresponding to an adjusted seroprevalence rate of 40%. Conclusions: During the second year of the pandemic, seropositivity rates were highest among young adults, particularly in the western regions, and lowest among children and adolescents. These findings point out variations in exposure across age groups and geographic areas. Full article

Background: Human milk (HM) provides critical immunological support to neonates, serving as a key component of passive immunity during early life. Objectives: The main aim of this cohort study was to compare the concentrations of lactoferrin (Lf), secretory immunoglobulin A (SIgA), C-reactive protein (CRP), and their ratios to total protein levels in the colostrum of postpartum women infected with SARS-CoV-2 and healthy controls. Methods: Colostrum samples (3–5 mL) were collected from 40 mothers (20 infected, 20 healthy) during the first wave of the COVID-19 pandemic in Poland. Concentrations of Lf, SIgA, and CRP were analyzed using ELISA, and total protein content was measured using the bicinchoninic acid assay (BCA). Results: The presence of specific anti-SARS-CoV-2 SIgA antibodies was assessed via cassette serological lateral flow detection tests. Significant differences were observed in Lf (p = 0.04) and SIgA (p = 0.03) concentrations, both lower in the COVID-19 group. Lactoferrin medians were 12.30 g/L (infected) and 14.95 g/L (healthy), and for SIgA: 9.15 g/L vs. 15.01 g/L, respectively. No significant difference was found in CRP levels. Interestingly, the Lf/Protein ratio was significantly higher in the infected group (p = 0.03), whereas the SIgA/Protein ratio did not differ. Furthermore, 75% of infected mothers had positive anti-SARS-CoV-2 SIgA results. These mothers also showed a higher Lf/Protein ratio. Among healthy controls, 90% had negative test results. Conclusions: These findings suggest a potential compensatory role of lactoferrin in the nonspecific immune response to SARS-CoV-2, though stress-related reductions in SIgA levels cannot be excluded. Full article