Objective: This retrospective study aimed to investigate the impact of COVID-19 vaccination on Bulgarian patient cohorts with uncomplicated diabetes mellitus type 2 as the only documented chronic comorbidity. We conducted a comparison of fully vaccinated and non-vaccinated populations, considering gender, age groups and vaccine type, across ambulatory, hospital, and ICU settings. Design: Between March 2020 and June 2022, a comprehensive retrospective analysis was conducted on a national level, utilizing data from the Ministry of Health of the Republic of Bulgaria database obtained after a formal written request. The study included a total of 1,126,946 confirmed COVID-19 patients. Results: Among the 1,126,946 confirmed COVID-19 patients, 3,792 individuals (0.33% of the total confirmed cases) had diabetes mellitus as a single chronic condition. Among the 247,441 hospitalized COVID-19 cases, 1,382 patients (0.56% of the total) had type 2 diabetes mellitus. Notably, the majority of patients requiring hospitalization due to supplemental oxygen requirement were unvaccinated women aged between 60 and 69, accounting for 240 patients. The highest mortality rates were observed in both unvaccinated men and women aged between 70 and 79, with 88 patients in each group. Statistical analysis revealed significant findings in favor of reduced rates of ambulatory care [OR = 0.76 (95% CI 0.6471 to 0.8891); p = 0.0006], intensive care admission [OR = 0.38 (95% CI 0.2698 to 0.5282); p < 0.0001], in-hospital mortality [OR = 0.18 (95% CI 0.0864 to 0.3604); p < 0.0001], and ICU-related mortality [OR = 0.17 (95% CI 0.0893 to 0.3436); p < 0.0001]. The vaccinated cohorts who received BNT162b2 demonstrated the lowest observed death rates, with 9 deaths out of 485 individuals (1.8%) across all age groups. Conclusion: In conclusion, this retrospective analysis indicates reduced mortality in patients with uncomplicated type II diabetes mellitus who received vaccination against SARS-CoV-2. Vaccinated individuals also showed significant reduction in ICU admissions.

The long-term impact of SARS-CoV-2 infection and vaccination in patients with solid malignancies remains incompletely defined, particularly with respect to long-term oncologic outcomes and interactions with systemic anticancer therapies. We conducted a nationwide, retrospective real-world cohort study using data from the Bulgarian Ministry of Health's United Information Portal. Adult patients (n = 1797) with solid malignancies who survived hospitalization for COVID-19 between March 2020 and June 2022 were included and followed through November 2025. Overall survival (OS) was evaluated according to vaccination status, vaccine platform (mRNA vs vector-based), primary tumor localization, and oncologic treatment modality. Multivariable logistic regression and propensity score matching were applied to adjust for demographic and clinical confounders. The study was conducted in accordance with ESMO-GROW guidelines. After a median follow-up of 48.6 months, mRNA-based vaccination was independently associated with lower long-term mortality (median OS, 43.6 months) compared with vector-based vaccination (34.9 months) or no vaccination (34.5 months) (OR, 0.41; 95% CI, 0.28-0.61; P < 0.0001). The survival benefit was most pronounced among patients receiving immune checkpoint inhibitors, particularly in lung cancer, where combined mRNA vaccination and immunotherapy was associated with superior outcomes (18.9% vs 31.1%; OR, 0.45; 95% CI, 0.20-0.98; P = 0.036). Results were consistent across multivariable and propensity score-matched analyses. In this large national real-world cohort with nearly five years of follow-up, mRNA-based COVID-19 vaccination was independently associated with improved long-term survival in patients with solid malignancies who survived COVID-19 hospitalization, supporting durable protective effects and suggesting a potential immunomodulatory interaction with immune checkpoint inhibition.

SPR has been recently established as a powerful tool for studying various cellular processes in real time and without the use of labeling agents. So far, all studies in this area have been performed using the Kretschmann method for SPR excitation. In our studies, we used grating-based SPR. Here, we investigated the feasibility of this approach in a cell-based assay applied for antiviral drug screening. It was found that the continuous-flow SPR detection used in the conventional SPR can be replaced by sequential signal measurements of SPR slides removed from the medium at fixed hours after seeding. A protocol ensuring correct measurements was established. SPR detection was performed up to 48 h after seeding the VERO E6 cell line in three experiments, in which the cells were (i) compound-untreated, (ii) compound-treated, and (iii) infected with human coronavirus type 229E and compound-treated. Therefore, the temporal variation in the SPR signal was determined, induced by the cell coverage on the slide, the compound toxicity, and its antiviral action. MTT analysis and microscopic observations were used as reference methods. The remarkable agreement found in the results of SPR detection proved the effectiveness and reliability of grating-based SPR applied in cell-based assays.

Central nervous system (CNS) infections caused by SARS-CoV-2 are uncommon. This case report describes the clinical progression of a 92-year-old female who developed a persistent neuroinfection associated with SARS-CoV-2. The patient initially presented with progressive fatigue, catarrhal symptoms, and a fever (38.6 °C). Initial laboratory findings revealed hypoxemia (O₂ saturation 79.8%), acidosis (pH 7.3), an elevated C-reactive protein (CRP) level of 14.8 mg/L, and a high D-dimer level (2.15 µg/mL). Nasopharyngeal (NP) antigen and RT-PCR tests confirmed SARS-CoV-2 infection, and an NP swab also detected penicillin- and ampicillin-resistant Staphylococcus aureus. She was admitted for conservative management, including oxygen supplementation, IV fluids, and prophylactic anticoagulation. Subsequently, she developed neurological symptoms—lethargy, discoordination, and impaired communication—without signs of meningism. Cerebrospinal fluid (CSF) analysis identified SARS-CoV-2 RNA (Ct = 29) on RT-PCR, while bacterial cultures remained negative. Treatment was intensified to include 10% mannitol, dexamethasone, and empiric ceftriaxone. Despite these interventions, the patient remained somnolent, with a Glasgow Coma Scale (GCS) score of 10. Upon discharge, her GCS had improved to 14; however, she continued to experience lethargy and cognitive issues, commonly described as “brain fog”. Inflammatory markers remained elevated (CRP 23 mg/L) and repeat RT-PCR of CSF confirmed a persistent SARS-CoV-2 presence (Ct = 31). This case underscores the potential for SARS-CoV-2 to cause prolonged CNS involvement, leading to persistent neurological impairment despite standard therapy. Further research is essential to clarify the pathophysiology of and determine optimal management for SARS-CoV-2 neuroinfections.

Background: Anti-N-methyl-D-aspartate receptor (anti-NMDAR) encephalitis is an autoimmune disorder frequently associated with ovarian teratomas in young women. Although infectious triggers have been proposed to contribute to immune activation, direct evidence linking viral presence within tumor tissue to disease pathogenesis remains limited. Case Presentation: An 18-year-old woman presented with acute neuropsychiatric symptoms, fever, gastrointestinal prodrome, and rapidly progressive behavioral disturbance progressing to encephalopathy. Cerebrospinal fluid and blood test results, together with clinical features, supported the diagnosis of anti-NMDAR encephalitis. Imaging identified an ovarian mass, and surgical resection was performed. Histopathology confirmed a mature teratoma containing neuroglial elements. Molecular analysis detected parvovirus B19 DNA within the resected teratomatous tissue. No systemic viremia or active central nervous system viral infection was identified. The patient received immunotherapy combined with tumor removal, with subsequent clinical improvement. Discussion: Ovarian teratomas remain a critical etiologic factor in anti-NMDAR encephalitis and mandate prompt surgical management. Detection of B19 viral DNA within teratomatous neuroglial tissue raises the hypothesis that viral persistence could enhance local immune activation and autoantibody generation. However, in this case polymerase chain reaction positivity does not indicate active infection, and the biological significance of this finding remains uncertain. Conclusions: This case documents rare detection of B19V DNA within an ovarian teratomatous tissue in anti-NMDAR encephalitis. The observation is hypothesis-generating rather than causal; established management priorities remain immunotherapy and tumor resection, and viral nucleic acid detection should be interpreted within the broader clinical context.