Search Results (313)

Background/Objectives: Post-COVID-19 condition involves heterogeneous, multisystem symptoms with uncertain recovery. We characterized symptom trajectories from hospitalization to approximately 4 weeks and to 6–8 months and compared the 6–8-month symptom burden with season-matched controls, accounting for serology-identified, previously unrecognized infections. Methods: An individually pair-matched case–control study of adults with RT-PCR–confirmed SARS-CoV-2 and population controls from the Bialystok PLUS cohort, matched on age, sex and a two-month visit window, was performed. All participants underwent anti-nucleocapsid serology. Hospitalized cases were reassessed at approximately 4 weeks and 6–8 months. Cross-sectional outcomes used non-parametric tests and multivariable regression; longitudinal change used paired tests and generalized estimating equations. Results: We included 402 adults (201 post-COVID-19; 201 controls). In hospitalized cases, respiratory symptoms declined rapidly by approximately 4 weeks and remained low at 6–8 months; smell/taste recovered more slowly; fatigue improved modestly; anxiety changed minimally. At 6–8 months, total symptom counts were higher in post-COVID-19 than in controls (median 4 vs. 2), with serology-positive controls intermediate (median 3). Excess burden was concentrated in non-respiratory domains (fatigue, neurocognitive, cardiovascular, and dermatologic), whereas respiratory differences were not significant. In the multivariable model, female sex remained an independent predictor of higher multisystem burden, whereas age, body mass index, hospitalization, and acute biomarker severity were not associated. Conclusions: Six to eight months after symptomatic COVID-19, multisystem symptom burden remains substantial relative to season-matched controls, despite substantial resolution of respiratory complaints. Serology-based identification of previously unrecognized infections indicates an intermediate burden and can guide targeted follow-up. Full article

Background and Objectives: Healthcare workers are at heightened risk of SARS-CoV-2 infection. Understanding the duration and protective value of vaccine-induced immunity is critical to inform booster strategies. This study investigates longitudinal dynamics of anti-SARS-CoV-2 receptor-binding domain IgG (anti-RBD IgG) antibodies and their association with infection risk among vaccinated healthcare workers. Materials and Methods: A prospective cohort study was conducted at Vilnius University Hospital Santaros Klinikos, Lithuania. A total of 1778 healthcare workers who completed a primary COVID-19 vaccination series were followed. Blood samples were collected every three months to measure anti-RBD IgG levels. Participants also received up to three booster doses. COVID-19 was identified by PCR, antigen tests, or positive anti-nucleocapsid IgG. For serologically detected cases, infection timing was assigned to the interval between study visits. Antibody dynamics were analyzed across vaccination stages, time, age groups, and circulating SARS-CoV-2 variants. Results: Anti-RBD IgG titers peaked in the first quarter after primary vaccination (mean 7904 AU/mL), declined sharply by quarters 2–3, and rose substantially after booster doses. Following the first booster, titers increased to ~12,598 AU/mL in quarter 1 and continued rising through quarter 3. The highest levels were observed after the second booster (24,456 AU/mL in Q1), followed by gradual decline. A high-titer plateau persisted from quarters 6 to 9 (~21,000 AU/mL), followed by decline in quarters 10–11 and partial rebound in Q12. Approximately 49.6% of participants experienced COVID-19 during follow-up. Antibody response patterns were similar across age groups, with only minor transient differences. Conclusions: COVID-19 booster doses significantly enhance and prolong humoral immunity in healthcare workers compared with the primary vaccination series. However, antibody waning over time emphasizes the need for timely boosters, particularly during periods of variant circulation. These findings support continued booster vaccination and monitoring of long-term immune protection, although anti-RBD IgG should be interpreted as a surrogate marker of humoral rather than overall immunity. Full article

Objective: Dental professionals are routinely exposed to infectious agents through contact with blood, saliva, and aerosols. This cross-sectional survey aimed to evaluate and compare knowledge, attitudes, and self-reported practices related to infectious diseases among dental students and practicing dentists in the post-COVID era. Methods: This web-based cross-sectional survey was conducted between January and March 2024 at a single dental faculty. Fourth- and fifth-year dental students and practicing dentists were invited to participate. A 30-item questionnaire assessed knowledge of infectious disease transmission and immunological markers (Questions Q1–Q19), as well as attitudes and self-reported practices toward patients with infectious diseases (Q20–Q30). Descriptive statistics were calculated, and comparisons between groups were performed using Pearson’s chi-square or Fisher’s exact tests (α = 0.05). Internal consistency of the questionnaire was acceptable (Cronbach’s alpha: 0.81 for knowledge items and 0.88 for attitude/practice items). Results: A total of 221 dental students and 33 dentists were included in the final analysis. Both groups demonstrated high awareness of respiratory transmission routes for COVID-19 and influenza. In contrast, recognition of bloodborne transmission pathways was limited, with approximately half of participants identifying blood contact and blood-contaminated instruments as potential sources of infection. Significant differences were observed between students and dentists in the interpretation of SARS-CoV-2 IgG antibodies, with dentists more frequently associating IgG positivity with prior infection (p = 0.009) and immunity (p < 0.001). Cautious behavior toward treating patients with infectious diseases was common in both groups, whereas reluctance to provide treatment and lower self-perceived knowledge were more frequently reported among students. Conclusions: Despite adequate awareness of respiratory infection transmission, important deficiencies persist in bloodborne pathogen knowledge, serological interpretation, and confidence in managing infected patients, particularly among dental students. These findings underscore the need for targeted, practice-oriented infection control education that integrates immunological principles and hands-on training to enhance clinical preparedness in the post-COVID era. Full article

The COVID 19 pandemic may have influenced smoking behaviours, including decisions to quit smoking. This study aimed to investigate smoking cessation following the first two waves of the COVID-19 pandemic in Switzerland and to assess whether cessation differed according to participants’ SARS-CoV-2–related experiences. Data from SérocoViD, a Swiss repeated cross-sectional study comprising five surveys in the canton of Vaud, was used. A total of 2454 participants aged 15 years and older from the first (May–July 2020) and third (February 2021) surveys were included. Association between SARS-CoV-2 infection experiences and cigarette smoking cessation were analyzed using logistic regression; both factors were unadjusted and adjusted for age and gender. Overall, 21.2% of participants reported being ex-smokers, but only a small proportion of the entire study population (i.e., including both smokers and non-smokers) reported quitting during the pandemic (0.5% in the first sample, 1.5% in the second). Participants who were smokers before the pandemic and had undergone diagnostic testing for SARS-CoV-2 showed a trend toward smoking cessation during the pandemic (non-adjusted odds ratio = 2.15; 95% confidence interval: 0.79–5.87). No such trends were found with a positive diagnostic test or serological result, or with COVID-19-like symptoms. These findings suggest that individuals seeking testing may be more health-conscious, potentially contributing to smoking cessation. For these individuals, the pandemic may represent a critical opportunity to promote smoking cessation, which should be leveraged by healthcare professionals and public health policies. Full article

Vector-borne parasites might be transmitted through transfusion, notably Plasmodium spp. and Trypanosoma cruzi. Prevention strategies include blood donor screening, deferral, and blood unit treatment by pathogen inactivation methods. At the end of 2015, in line with European guidelines, Italian legislation introduced a questionnaire to identify donors at risk and their screening by serological methods. In early 2016, the Laboratory of Parasitology at Pisa University Hospital started the serological analysis of donors at risk, referring to Transfusion Services located in northwestern Tuscany. The aim of the present study was to describe the prevalence of seropositive donors observed during 8 years of screening. Donors at risk of transmitting malaria were screened by ELISA (Enzyme Linked Immunosorbent Assay). The DRG ELISA kit was employed until 2020, when it was substituted by the Euroimmun ELISA kit based on the results of a comparative evaluation of available commercial kits. Seropositive donors were offered the possibility of Plasmodium DNA testing by Loop-Mediated AMPlification (LAMP) to exclude current infection. Donors at risk of transmitting Chagas disease were screened by ICT employing recombinant antigen until 2021, when it was substituted by ELISA employing lysate antigen because of its higher accuracy. Seropositive donors were further tested by CLIA, and WB was performed in case of discordant results, according to WHO guidelines for diagnosis of chronic Chagas disease. A total of 3754 donors were tested for anti-Plasmodium antibodies, revealing a 6.8% (95% CI = 6.1–7.7%) seroprevalence. Seropositivity was higher among donors from Sub-Saharan Africa (42.9%; 95% CI = 36.1–49.9%) and Southeast Asia (10.6%; 95% CI = 6.7–16.4%). A lower seropositivity was observed when employing Euroimmun ELISA (4.8; 95% CI = 3.8–5.9%) than DRG ELISA (8.2%; 95% CI = 7.1–9.3%). Seropositivity dropped to 3.6% (95% CI = 2.4–5.6) in 2020, likely because of travel restrictions during the COVID-19 pandemic. None of the tested seropositive donors (n = 20) tested positive for Plasmodium DNA LAMP testing. A high proportion of seroreversion was observed after one year of testing. Among 4285 donors tested for anti-T. cruzi antibodies seroprevalence was 0.7% (95% CI = 0.5–1.1%), a higher value than what was observed in a recent national survey. All seropositive donors were born in Europe or Latin America. Seropositivity was apparently lower with ELISA (0.5%, 95% CI = 0.2–1.2%) than ICT (0.8%, 95% CI = 0.6–1.2%), possibly due to ELISA’s higher specificity, although the difference is not significant. No confirmed cases of chronic Chagas disease were identified. The study emphasizes the importance of defining the serological test employed for screening and the need to confirm seropositive results with further testing. The high seroreversion observed in the study suggests repeating seropositive donor screening after a year to minimize deferral and blood unit loss. Full article

The emergence and spread of coronavirus infections have created a necessity to develop serological methods for assessing population immunity. The enzyme-linked immunosorbent assay (ELISA) remains one of the most accessible and informative approaches for these purposes. The choice of recombinant proteins plays an important role in the sensitivity and specificity of the test system, and in this regard, the creation of a domestic ELISA based on the chimeric SM protein to the SARS-CoV-2 virus is relevant. In this work, a recombinant chimeric SM protein expressed in the E. coli system and purified using metal-affinity chromatography on Ni-NTA agarose was constructed and presented for the first time. An ELISA test system was developed and tested using panels of positive and negative sera, including samples obtained before the COVID-19 pandemic. The obtained sensitivity (90.48%) and specificity (93.65%) indicators with a ROC curve AUC = 0.9623 (OD450 = 0.213) indicate the diagnostic accuracy of the test system. The positive diagnostic ratio (LR+) = 14.25.0 indicates the reliability of a positive result. The domestically developed ELISA test system can be used for serological monitoring and assessment of the immune status of the population. Full article

Background/Objectives: COVID-19 and long COVID remain prevalent, with household transmission being an important mode of spread. To quantify household transmission of subclinical SARS-COV-2 infection and identify sociodemographic risk factors that may explain disparities in transmission, we conducted a case-ascertained antibody surveillance study of households in Cincinnati, Ohio. Methods: A partnership was formed between the Cincinnati Health Department and Cincinnati Children’s Hospital Medical Center. The Health Department identified cases of COVID-19. Infected individuals, along with their household contacts (n = 245), completed multiple questionnaires about symptoms, demographics, psychosocial (Adverse Childhood Experiences Scale and Everyday Discrimination Scale) and social risk factors, and conditions before and during the pandemic. In addition, they completed a non-fasting blood draw for IgG, IgM, IgA, and nucleocapsid protein serology testing. Results: Household contacts experienced few symptoms of COVID-19. However, according to the presence of the nucleocapsid protein, nearly 50% contracted the SARS-CoV-2 virus. This rate was similar by vaccination status but it was higher for household contacts who experienced high levels of early life adversity compared with those with lower levels. Conclusions: Our results confirm the high transmission of subclinical disease among household contacts, which may vary due to psychosocial factors. This reinforces the importance of isolating cases to prevent transmission, regardless of vaccination status. Full article

Since the beginning of the 21st century, major epidemics and pandemics such as SARS, H1N1pdm09, Ebola, and COVID-19 have repeatedly challenged global systems of disease diagnostics and control. These crises exposed the weaknesses of traditional diagnostic models, including long turnaround times, uneven resource distribution, and supply chain bottlenecks. As a result, there is an urgent need for more advanced diagnostic technologies and integrated diagnostics strategies. Our review summarizes key lessons learned from four recent major outbreaks and highlights advances in diagnostic technologies. Among these, molecular techniques such as loop-mediated isothermal amplification (LAMP), transcription-mediated amplification (TMA), recombinase polymerase amplification (RPA), and droplet digital polymerase chain reaction (ddPCR) have demonstrated significant advantages and are increasingly becoming core components of the detection framework. Antigen testing plays a critical role in rapid screening, particularly in settings such as schools, workplaces, and communities. Serological assays provide unique value for retrospective outbreak analysis and assessing population immunity. Next-generation sequencing (NGS) has become a powerful tool for identifying novel pathogens and monitoring viral mutations. Furthermore, point-of-care testing (POCT), enhanced by miniaturization, biosensing, and artificial intelligence (AI), has extended diagnostic capacity to the front lines of epidemic control. In summary, the future of epidemic and pandemic response will not depend on a single technology, but rather on a multi-layered and complementary system. By combining laboratory diagnostics, distributed screening, and real-time monitoring, this system will form a global diagnostic network capable of rapid response, ensuring preparedness for the next global health crisis. Full article

Autonomic nervous system (ANS) dysfunction has emerged as a central feature of post-infectious syndromes, including post-COVID syndrome (PCS), chronic fatigue syndrome (CFS), and late-stage Lyme disease. This cross-sectional study included 1036 patients evaluated in the Neurocardiological Laboratory of the Institute for Cardiovascular Diseases “Dedinje,” divided into four groups: PCS, CFS after COVID-19, CFS of insidious onset, and Lyme disease. All patients underwent head-up tilt testing (HUTT), and serological testing was performed in accredited institutions. The Lyme disease group demonstrated the highest prevalence of positive HUTT responses and a significantly greater frequency of orthostatic hypotension and syncope. Approximately 50–65% of patients in the PCS and Lyme groups were positive for IgM antibodies against at least one microorganism, with more than 10% showing positivity for three or more pathogens. Logistic regression analysis revealed that, beyond classical hemodynamic parameters, antibody status served as a significant predictor of HUTT outcomes, with specific associations identified for HSV-1, HHV-6, Coxiella burnetii, Toxoplasma gondii, and Borrelia spp. Multinomial regression further indicated that negative IgG antibodies, particularly to HSV-1 and VZV, predicted Lyme disease group membership. These findings support the hypothesis that ANS dysfunction in post-infectious syndromes may be driven by persistent or prior infections, highlighting the need for integrative diagnostic approaches. Full article

Serological testing for SARS-CoV-2-specific antibodies, particularly those targeting the nucleocapsid protein, plays a key role in assessing past infection and estimating population-level seroprevalence. The seroprevalence of nucleocapsid antibodies against SARS-CoV-2 was evaluated in 1048 blood donors using the Elecsys Anti-SARS-CoV-2 electrochemiluminescence immunoassay. Participants completed a questionnaire to assess risk factors, symptoms during SARS-CoV-2 infection and vaccination status. The overall SARS-CoV-2 seroprevalence was 89.69%. Seroprevalence was not significantly associated with gender or age. In multivariate logistic regression, most investigated risk factors showed no significant association with seroprevalence. However, residence area and vaccination status were independently associated with SARS-CoV-2 seropositivity. Donors from rural areas had significantly higher odds of seropositivity (aOR = 1.68; 95% CI: 1.01–2.79; p = 0.045) compared to those from urban areas. Unvaccinated individuals were more likely to test positive for SARS-CoV-2 compared to vaccinated participants (aOR: 2.59; 95% CI: 1.35–4.99; p = 0.004). After three years of the COVID-19 pandemic, the prevalence of SARS-CoV-2 among blood donors was remarkably high, indicating that the vast majority of this population group had been exposed to the virus. This study highlights the risk factors for SARS-CoV-2 infection and the differences in antibody prevalence between vaccinated and unvaccinated individuals. Our findings underscore the pivotal role of vaccination in controlling the pandemic and provide valuable insights for policymakers in designing targeted strategies to curb future SARS-CoV-2 transmission. Full article

Background: Currently available immunological tests for SARS-CoV-2 assess only antibody responses. Despite the growing evidence that T cells play a crucial role in protection, especially against emerging viral variants, no routine test is available to determine T cell immunity. The prognostic value of SARS-CoV-2-specific antibodies for determining whether individuals are immune and protected against disease remains uncertain. This is in part due to the following: (a) specificity and limitations such as the sensitivity of antibody tests, and (b) the lack of correlation between antibody titers (quantity) and the antiviral function of antibodies (quality). Approximately a quarter of SARS-CoV-2-infected patients with symptoms fail to show seroconversion in serological assays. Methods: The current report describes the development and application of a whole-blood-based assay to detect previous exposure to SARS-CoV-2. Whole blood is stimulated with SARS-CoV-2-derived peptides identified during assay development and stimulation-induced cytokines quantified using a multiplex testing platform. The resulting cytokine profiles are generated using computational tools to identify previous exposure to the virus. Results: The application of the assay revealed a lack of self-awareness of individuals’ COVID-19 infection history and demonstrated the value of this new assay to assess the prevalence of SARS-CoV-2 exposure history and immunity in populations. Conclusions: Positive responses in this assay can facilitate the identification of underlying causes of unexplained symptoms and provide clinically actionable insights for healthcare applications, including in the continued conundrum of post-acute sequela of SARS-CoV-2 infection (PASC or “long COVID”), for which both diagnosis and management remain challenging. Full article

The ongoing COVID-19 pandemic has underscored the urgent need for rapid, sensitive, and versatile diagnostic tools. In this study, we developed a nanogold-based lateral flow immunoassay (LFIA) capable of detecting both SARS-CoV-2 nucleocapsid (N) protein antigens and anti-N IgG antibodies at the point of care. Following optimization of colloidal gold nanoparticle size, pH, and protein conjugation parameters, LFIA strips were assembled in two formats: a competitive assay for antigen detection and a sandwich assay for antibody detection. In the competitive format, gold nanoparticles (AuNPs)-conjugated N protein were used to detect varying concentrations of free N protein. The test line signal inversely correlated with antigen concentration, confirming the assay’s specificity and effectiveness. For antibody detection, the sandwich LFIA format employed immobilized anti-human IgG to capture anti-N antibodies in serum samples from COVID-19 patients. Strong test line signals were observed in samples collected ≥11 days post-symptom onset, indicating a time-dependent increase in IgG detectability. These results demonstrate that the AuNP-based LFIA platform provides a flexible, rapid, and low-cost diagnostic solution, suitable for both early antigen detection and serological monitoring during SARS-CoV-2 infection and recovery. Full article

Background/Objectives: The COVID-19 pandemic and the development of vaccines provided the opportunity to monitor disease prevalence and outcomes, vaccinations, their side effects and serological responses in patients with inflammatory bowel disease (IBD). Methods: IBD patients of the outpatient clinic at the University Hospital Heidelberg who completed at least one questionnaire on COVID-19 and related vaccinations from July 2021 to August 2022 were included. Spike-IgG antibody titres were determined. Friedman tests, Wilcoxon signed-rank tests and Kruskal–Wallis tests were used for comparisons. The influence of IBD therapy was analysed using linear models with mixed effects. Results: The cohort included 520 patients (269 females, mean age = 45.3 years, 60.6% with Crohn’s disease, 35.4% with ulcerative colitis, and 4.0% with unclassified IBD). Four hundred eighty patients (92.3%) received at least one COVID-19 vaccination, and 154 patients (29.6%) were infected by SARS-CoV-2. Among all of them, 94.4% achieved seroconversion. Triple-vaccinated patients with additional SARS-CoV-2 infection developed the highest serological responses (χ² = 16.51, p < 0.001, df = 3). An antibody decay over time was observed after the second (p < 0.001) and third vaccinations (p < 0.001). Regarding individual IBD medications, no differences in mean titres were found after two (χ² = 6.60, p = 0.36, df = 6) versus three vaccinations (χ² = 4.97, p = 0.42, df = 5). Linear models with mixed effects revealed no influence of IBD therapies on serological responses. Conclusions: The highest serological responses were observed in IBD patients after three vaccinations plus SARS-CoV-2 infection without significant differences between IBD therapies. 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: 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