At the end of 2020, population-based vaccination programs with new generation mRNA-based vaccines began almost all over the world. The aim of the study was to evaluate the titer of anti-SARS-CoV-2 IgG antibodies against the S1 subunit of the virus’s spike protein as a marker of the humoral response in 477 patients and the concentration of interferon-gamma as an indicator of cellular response in 28 individuals. In our studies, we used serological enzyme-linked immunosorbent assays. IgG was measured in weeks 2 and 3 after the first dose and 1–5 weeks after the second dose of an mRNA vaccine in seropositive and seronegative individuals as well as in symptomatic and asymptomatic convalescents. High levels of antibodies were observed in 98% of our vaccinated cohort, and the presence of protective T cells was confirmed in the blood samples of all participants. The humoral immune response is diversified and is visible as early as 2–3 weeks after the first dose of the mRNA vaccine. The level of protection increased significantly after the second dose, with the increase being much greater in pre-vaccine healthy subjects and less in convalescents. In the second and third weeks after the second dose, the concentration of IgG antibodies was the highest, and in the following weeks, it decreased gradually. Regular serological measurements on eight subjects show that antibody titers are lower four months after vaccination than before the second dose.

Background: COVID-19 vaccines induce a differentiated humoral and cellular response, and one of the comparable parameters of the vaccine response is the determination of IgG antibodies. Materials and Methods: Concentrations of IgG anti-SARS-CoV-2 antibodies were analyzed at three time points (at the beginning of May, at the end of June and at the end of September). Serum samples were obtained from 954 employees of the Nicolaus Copernicus University in Toruń (a total of three samples each were obtained from 511 vaccinated participants). IgG antibody concentrations were determined by enzyme immunoassay. The statistical analysis included comparisons between vaccines, between convalescents and COVID-19 non-patients, between individual measurements and included the gender, age and blood groups of participants. Results: There were significant differences in antibody levels between mRNA and vector vaccines. People vaccinated with mRNA-1273 achieved the highest levels of antibodies, regardless of the time since full vaccination. People vaccinated with ChAdOx1 nCoV-2019 produced several times lower antibody levels compared to the mRNA vaccines, while the antibody levels were more stable. In the case of each of the vaccines, the factor having the strongest impact on the level and stability of the IgG antibody titers was previous SARS-CoV-2 infection. There were no significant correlations with age, gender and blood type. Summary: mRNA vaccines induce a stronger humoral response of the immune system with the fastest loss of antibodies over time.

Background: The presented research made it possible to obtain the characteristics of changes in anti-SARS-CoV-2 IgG within one year of vaccination in healthcare workers. Materials and Methods: The research group consisted of 18,610 participants represented by medical and administration staff. IgG antibody concentrations were determined by ELISA. Results: At 5–8 months after full vaccination, the levels of anti-SARS-CoV-2 IgG with equal vaccines were similar. The exception was JNJ-78436735, for which IgG levels were significantly lower. In the 9th month after vaccination, an increase in the anti-SARS-CoV-2 IgG level, suggesting asymptomatic infection, was observed in a large group of participants. Significantly higher levels of anti-SARS-CoV-2 IgG antibodies were observed after the booster dose compared to the second dose. The increase in antibodies was observed already around the 5th day after the injection of the booster dose, and was maximized at approximately the 14th day. Conclusion: The cut-off date for protection against the disease seems to be the period 8–9 months from the vaccination for mRNA vaccines and 5–6 months for vector vaccines. The introduction of a booster dose was the right decision, which could have a real impact on restricting the further transmission of the virus.

Growing evidence indicates that the gut microbiota is a central regulator of systemic immunity, acting through epithelial barrier integrity, microbial metabolites, and bidirectional signaling with innate and adaptive immune cells. Within this framework, probiotics have attracted substantial interest as tools for immune modulation; however, their effects are not uniform and should not be generalized across species or formulations. This review synthesizes current evidence on the gut microbiota–immune axis and examines how defined probiotic strains influence immune homeostasis, inflammation, and clinical outcomes. Particular emphasis is placed on strain-specific effects among lactic acid bacteria, bifidobacteria, yeast probiotics, and emerging nontraditional candidates, with attention to mechanisms involving cytokine signaling, regulatory T-cell induction, nuclear factor kappa B (NF-κB) modulation, toll-like receptor (TLR) pathways, short-chain fatty acids (SCFAs), tryptophan metabolites, and bile-acid-dependent signaling. The available literature indicates that the most meaningful immunological effects arise from precisely characterized strains acting in specific host contexts, whereas inconsistent trial design, small sample sizes, variable dosing, and poor strain resolution continue to limit translation. Overall, current data support a shift from generic probiotic use toward mechanism-based, strain-specific, and increasingly personalized strategies for immune modulation.

Sarcopenia is a progressive skeletal muscle disorder in which clinically relevant muscle failure is expressed primarily as reduced muscle strength, with low muscle quantity or quality used to confirm the diagnosis and impaired physical performance indicating greater severity in the EWGSOP2 (European Working Group on Sarcopenia in Older People 2) framework. This narrative review first defines the clinical phenotype and its current diagnostic operationalization and then uses an author-proposed five-pillar framework: energy, structure, regeneration, neuromuscular control, and systemic communication, to organize the interacting biological mechanisms that may generate that phenotype. The framework is intended as a translational heuristic rather than a validated classification and is positioned within broader geroscience and hallmarks-of-ageing concepts. Particular emphasis is placed on the distinction between muscle mass, strength, power, and physical performance; context-dependent mTORC1 signaling; the limited specificity of candidate biomarkers; and the uncertain causal direction of several mechanistic associations. Resistance exercise and adequate energy and protein intake remain the foundations of management, whereas pharmacological and regenerative strategies have not yet demonstrated sufficiently consistent improvements in patient-relevant functional outcomes to replace these interventions. Linking biological mechanisms to measurable muscle failure may improve interpretation of current evidence and help define priorities for future mechanistic and clinical studies.