Impact of pre-vaccination active vitamin D levels on COVID-19 mRNA vaccine-induced immunity in a Japanese cohort.

Sustainable antibiotic reduction in poultry production with Pulsatilla saponins and herbal supplementation.

Oral immunization with engineered probiotics expressing tcdB protects mice against Clostridioides difficile infection.

Dietary iron overload exacerbates intestinal damage induced by Eimeria tenella infection in broilers via impaired barrier integrity and gut microbiota dysbiosis.

The search for probiotic strains with anti-inflammatory properties is an urgent problem in modern microbiology, immunology and biotechnology. Probiotic therapy is a new concept in dentistry. Probiotic drugs are available as a variety of commercial forms, including tablets, toothpaste, mouth rinses. Probiotics affect immune function by regulating local and systemic mechanisms, interacting with epithelial cells of the oral cavity, thereby enhancing the barrier function of the mucous membrane, both in healthy people and in patients with various dental disorders. The aim of this study was to evaluate the effect of the probiotic rinse aid “ImmunitDominos” upon secretion of pro- and anti-inflammatory cytokines, immunoglobulins and lysozyme in oral fluid of healthy people. The material for the study included 64 oral fluid samples obtained from conditionally healthy people aged 30 to 76 years divided into 2 groups during the study: 1, with initially low cytokine values in the oral fluid; and 2, without somatic diseases, but with high cytokine values. The ingredient composition of the mouthwash “ImmunitDominos” was represented by a dry concentrate of five probiotic strains of bifidobacteria (the content of bifidobacteria in one sachet package is at least 108 CFU/g). The mouthwash “ImmunitDominos” was used twice a day for 28 days. The levels of IgA, IgM, IgG (AO Vector-Best, Russia) and cytokines IFNγ, TNFα, IL-17, IL-6, IL-10, IL-1ra (Cytokine LLC, Russia) were determined in oral fluid samples of the subjects examined by the ELISA method; Lysozyme was assayed by a turbidimetric method. The use of a probiotic rinse aid in the subjects of group 1 did not affect the level of cytokines, but led to an increase in lysozyme contents. It was found that the subjects of the 2 group showed a decreased level of IgG and proinflammatory cytokines, especially IL-17, IL-6, TNFα, as well as an increase in the anti-inflammatory IL-1ra. The results obtained revealed the anti-inflammatory effect of the probiotic mouthwash “ImmunitDominos”, thus allowing to recommend it as a potentially preventive agent that increases the local protection of the oral cavity.

Introduction Selective immunoglobulin A deficiency (SIgAD) is the most common primary immunodeficiency. Although most patients remain asymptomatic, SIgAD is frequently associated with autoimmune and allergic diseases, while infections occur considerably less often than in common variable immunodeficiency (CVID). The aim of the study was to examine the prevalence of SIgAD among patients with inflammatory and autoimmune diseases, to characterise their infectious risk and immunological abnormalities, and to compare their clinical and laboratory parameters with those observed in CVID. The SIgAD was diagnosed when the serum sensitive IgA level was 0.7 g/l. Material and Methods Among patients treated for autoimmune/inflammatory conditions at the Rheumatology and Immunology Clinic of the University of Debrecen, SIgAD was confirmed in 33 patients (27 women, 6 men; average age 54.15 ±13.4 years, and average sensitive IgA 0.31 g/l). The CVID (defined as IgG 6 g/l with low IgA, IgM levels) was diagnosed in 10 patients (8 women, 2 men; average age 60.6 ±15.6 years). Results In the SIgAD group, recurrent non-severe infections (mainly upper respiratory and urinary tract infections) occurred in 11 patients (33.3%). Allergic diseases (asthma, pollen allergy, atopic dermatitis) were present in 19 cases (57.6%), and concomitant malignancy in 4 patients (12.1%). The underlying autoimmune diseases included rheumatoid arthritis (n = 12), systemic lupus erythematosus or rheumatoid arthritis–systemic lupus erythematosus overlap syndrome (n = 7), undifferentiated connective tissue disease (n = 8), spondyloarthropathy (n = 2), myositis (n = 1), polymyalgia rheumatica (n = 2), and scleromyxedema (n = 1). Allergic and celiac diseases occurred significantly more frequently in SIgAD than in CVID, whereas malignant diseases were significantly less common. Immunophenotypic analysis revealed that the proportion of CD8+ naïve T cells (40.44%) was significantly higher in SIgAD compared to CVID (34.4%, p = 0.05). The proportion of CD19 naïve B cells was significantly lower and showed a strong positive correlation with decreased IgA levels (R = 0.52, p = 0.003). In contrast, CD19+ IgM memory B cells were significantly increased and were associated with the more frequent occurrence of allergic and neoplastic diseases. Discussion Patients with SIgAD exhibit significant abnormalities in both humoral and cellular immune responses. Conclusions Determining the subtypes of T- and B-cells may contribute to a better understanding of disease pathogenesis and may help identify patients at increased risk for additional comorbidities.

ABSTRACT Neonatal IgM antibodies reflect an in utero immune response to Treponema pallidum and may offer added diagnostic value. This study evaluated the test performance of treponemal IgM levels measured by the research-use-only (RUO) Dual Path Platform (DPP) Syphilis TnT point-of-care (POC) assay for congenital syphilis (CS) risk stratification. Conducted from May 2023 to May 2025, this study tested neonatal serum samples from infants born to mothers with syphilis using the DPP Syphilis TnT RUO POC assay, which reports treponemal and nontreponemal IgM levels as relative light units (RLU). Neonates were classified as confirmed proven or highly probable CS , possible CS , or CS less likely per guidelines; 23 neonates without maternal syphilis served as controls. Treponemal IgM levels were compared across categories using nonparametric tests and ordinal logistic regression. Diagnostic performance used prespecified cutoffs, with agreement assessed against neonatal rapid plasma reagin (RPR). Twenty-two maternal-neonatal dyads were included. Mean treponemal IgM levels rose with CS severity, peaking in the high-risk group ( possible or confirmed proven/highly probable CS: 29.9 ± 20.6 RLU) versus CS less likely (17.5 ± 20.8 RLU) and controls (3.5 ± 0.8 RLU; P < 0.05). Higher IgM levels independently linked to elevated CS risk (OR 1.10 per 1 RLU; P = 0.0025). At ≥10 RLU cutoff, treponemal IgM detected 88.9% of high-risk neonates, with 76% agreement to neonatal RPR. The DPP Syphilis TnT RUO POC assay’s treponemal IgM levels discriminated CS risk categories effectively and may supplement current algorithms to improve neonatal CS stratification. IMPORTANCE Congenital syphilis (CS) continues to rise in the United States and globally, yet diagnosis at birth remains difficult because no single laboratory test definitively confirms infection in newborns. Clinical decisions often rely on maternal history and indirect serologic comparisons, which can result in both missed cases and unnecessary treatment of low-risk infants. IgM antibodies are produced by the fetus in response to infection in utero and therefore represent a biologically meaningful marker of congenital infection. This study evaluates the diagnostic potential of the Dual Path Platform Syphilis TnT research-use-only point-of-care assay to detect treponemal IgM in at-risk neonates. We demonstrate that IgM levels increase across CS less likely , possible CS , and confirmed proven or highly probable CS categories and are independently associated with disease risk. These findings provide early evidence that neonatal IgM testing may improve risk stratification and support more precise clinical decision-making in CS management.

The problem of antibiotic-resistant bacteria poses serious challenges for modern surgical dentistry, particularly in preventing purulent complications after the removal of impacted lower third molars. In response to this challenge, bacteriophages are being actively studied worldwide as one of the most promising solutions. Bacteriophages have the potential to effectively eliminate antibiotic-resistant bacteria, demonstrate a high safety profile, and offer a wide range of therapeutic applications. Purpose: Determination of the effect of complex antibiotic and phagotherapy on local immunity indicators in patients who underwent extraction of retained lower third molars. Materials and methods: The study involved 60 patients with retained lower third molars. After surgery, the patients were randomized into two groups: the first group (30 patients) received antibiotics to prevent complications, while the second group (30 patients) received a combination of antibiotics and polyvalent pyobacteriophage. To assess the dynamics of the immune response in the oral cavity, the levels of pro-inflammatory and anti-inflammatory cytokines, as well as immunoglobulins of classes A, G, and M, were measured before and 10 days after surgery. The obtained results were processed in accordance with medical statistics requirements using nonparametric analysis methods. Quantitative variables were assessed using the Mann-Whitney U-test (for independent samples) or the Wilcoxon T-test for connected samples. Differences between groups were considered significant at p 0.05. Results and discussion: The study revealed a decrease in the activity of inflammatory processes, which is confirmed by a decrease in the concentration of IL-1β and TNF in the oral fluid. At the same time, there was an increase in the anti-inflammatory response, which is manifested in an increase in the level of IL-10, as well as an activation of humoral immunity, which is expressed in an increase in the levels of IgA, IgG, and IgM. Conclusion: The obtained data indicate that the inclusion of bacteriophages in the therapeutic protocol of the postoperative period contributes to the positive modulation of the immune response in patients, demonstrating the beneficial effect of phage therapy on the immunological status in the postoperative period.

Background: X-linked hyper-IgM syndrome (X-HIGM) is a rare primary immunodeficiency disorder characterized by recurrent infections, hypogammaglobulinemia, and elevated IgM levels. The condition results from mutations in the CD40LG gene, which encodes CD40 ligand, a protein essential for B cell activation and immunoglobulin class switching. This study presents a clinical case of X-HIGM in a young child and highlights the effectiveness of immunoglobulin G replacement therapy in managing the disease.Methods: Whole-exome sequencing and Sanger sequencing were performed to identify the genetic cause of the patient’s recurrent infections. A hemizygous c.409+1_409+19del mutation was identified in the CD40LG gene, confirming the diagnosis of X-HIGM. Immunoglobulin G replacement therapy was administered to manage the patient’s condition.Result: Peripheral immunoglobulins confirmed the clinical observations, with low IgG and A but strikingly high IgM levels. Recurrent otitis media and pneumonia were common in early childhood. The genetic testing performed afterward confirmed that the mutation was present in the two affected siblings. This favorable clinical response with a decrease in the frequency of infections and the stability of the IgG levels over the time suggests that IgRT may have a long-term effective role in the management of a rare primary immunodeficiency. It also stresses the need for genetic workup for diagnosis, family counselling, and management of rare immunodeficiency syndromes.Conclusion: This case highlights the need for early diagnosis and treatment of X-HIGM. IgG replacement therapy is an effective option when stem cell transplantation is not possible or suitable.Keywords:Hyper-IgM syndrome, Primary immunodeficiency, Young children, Immunoglobulin G replacement therapy, CD40LG

Immune-mediated necrotizing myopathy (IMNM) is a severe autoimmune myopathy causing proximal muscle weakness. Its underlying immunopathogenesis remains incompletely understood, limiting the development of targeted therapies. To elucidate disease mechanisms and inform therapeutic strategies, this study characterized the peripheral immune profile of treatment-naïve IMNM patients. This retrospective study analyzed serum cytokine levels, complement proteins (C3, C4), immunoglobulins (IgA, IgG, and IgM), and peripheral blood lymphocyte subsets in 28 treatment-naïve IMNM patients during the active disease phase and 25 healthy controls at Tongji Hospital from August 2023 to March 2025. Compared with healthy controls, IMNM patients showed significantly elevated serum concentrations of interleukin-6 and interferon-γ (both p < 0.001). IgG and IgM levels were also markedly higher in the IMNM group (p = 0.003; p = 0.002). The number and percentage of B cells were significantly increased in IMNM patients (both p = 0.004). The number and percentage of CD8+ T cells were similarly elevated (p = 0.009; p = 0.004). In contrast, the proportion of CD4+ T cells was significantly reduced (p = 0.002), and the absolute count of natural killer cells was also significantly reduced (p = 0.004). IMNM exhibits a distinct peripheral immune landscape, characterized by enhanced humoral immunity potentially driven by CD8+ T cell-mediated mechanisms, accompanied by reduced circulating natural killer cells. These findings suggest potential biomarkers for disease activity and may inform targeted immunotherapies. Further studies are needed to validate these immune alterations and clarify their role in IMNM pathogenesis.

To estimate the residual risk of maternal-fetal transmission after primary cytomegalovirus (CMV) infection in the periconceptional period or the first trimester in women treated with valacyclovir, and to assess whether the presence of glycoprotein B2 (gB2)-specific immunoglobulin (Ig)-G antibodies on immunoblot analysis refines fetal risk prediction. This was a retrospective single-center study conducted at University Hospital Tübingen, Tübingen, Germany, between October 2023 and June 2025. Pregnant women with a primary CMV infection diagnosed < 14 weeks' gestation who received valacyclovir (8 g/day) were included in the study. The diagnosis of a recent primary CMV infection was based on maternal serology results, specifically positive anti-CMV-immunoglobulin (Ig)-G and -IgM levels, and low or intermediate IgG avidity. Additionally, prior to initiation of valacyclovir treatment, the presence or absence of glycoprotein B (gB)2-specific IgG antibodies was determined using a commercial line immunoblot. The primary outcome was maternal-fetal transmission of CMV detected at the time of second-trimester amniocentesis. Eighty-five women met the inclusion criteria, including 47 with periconceptional and 38 with first-trimester maternal CMV infection. Median maternal and gestational age at the time of diagnosis of primary maternal CMV infection were 33.1 (interquartile range (IQR), 29.9-34.9) years and 7.4 (IQR, 6.4-8.9) weeks, respectively. Amniocentesis was performed at a median gestational age of 20.6 (IQR, 20.1-21.0) weeks. Overall, maternal-fetal transmission was detected in 7/85 (8.2%) cases at the time of amniocentesis. All CMV transmissions occurred in women without gB2-specific IgG antibodies (7/55 (12.7%)), while no transmissions occurred in those with gB2-specific IgG antibodies (0/30 (0%)) (P = 0.048). In women with a primary CMV infection treated with valacyclovir, the presence of gB2-specific IgG antibodies on immunoblot analysis identifies a subgroup with a low residual risk of maternal-fetal transmission. Incorporating gB2-specific IgG antibodies status into risk stratification may improve patient counseling and clinical decision-making. © 2026 The Author(s). Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Evaluation of Helicobacter pylori infection and clinical features in multiple sclerosis patients coexisting with vitiligo: Case-series.

Synthetic detergents including Linear alkylbenzene sulfonates (LAS) and Branched alkylbenzene sulfonates (BAS) are commonly used in household and industrial cleaning products, yet their chronic toxicological effects on freshwater fish species remain inadequately explored. The current study investigates the sub-lethal effects of these synthetic detergents on hemato-biochemical profile of freshwater fish Labeo rohita. The 96-h LC50 values of LAS and BAS for the selected fish were calculated as 6.45mg/L and 8.31mg/L, respectively, using the probit analysis method. A total of 180 fish specimens were randomly subjected to a triplicate experimental setup, with 60 fish allocated to each replicate, marked as G0, G1, G2 ang G3 where G0 served as control while the remaining three groups were treated with LAS (3.22mg/L), BAS (4.15mg/L) and their binary mixture (LAS, 1.61mg/L + BAS, 2.7mg/L) respectively, for a period of 30days. Post exposure analysis revealed a significant reduction (p < 0.05) in the RBCs, hemoglobin, and hematocrit value with increase in WBCs and platelets count in detergents exposed fish, compared to control. Among endocrine hormones T3, T4 and insulin levels decreased significantly (p < 0.05), while TSH and Cortisol were increased in the detergents exposed fish. Blood levels of NO, IgM, and RB were significantly decreased (p < 0.05) in all detergent treated fish, whereas lysozyme activity was significantly increased only in the LAS and mixture detergent treated fish. Antioxidant biomarkers, including CAT, SOD, and GSH, were significantly decreased (p < 0.05), whereas MDA levels showed a marked increase in detergents exposed fish. Histopathological analysis identified substantial alterations in gill tissues across all the detergents exposed groups. Furthermore, genotoxic analysis demonstrated a significant (p < 0.05) increase in micronuclei (MNs) and erythrocytic nuclear abnormalities (ENAs), confirming the genotoxic potential of the tested detergents. These findings suggest that chronic exposure to commonly used detergents can disrupt multiple physiological systems in L. rohita, highlighting the potential ecological risks of detergent pollution in freshwater ecosystems.

Efficacy of fresh frozen plasma immunotherapy as an adjuvant treatment of neonatal sepsis in puppies.

Immune and protective effects of recombinant multi-epitopes vaccine against infectious spleen and kidney necrosis virus in pearl gentian grouper (♀Epinephelus fuscoguttatus × ♂Epinephelus lanceolatus).

The global restriction of antibiotic growth promoters (AGPs) has accelerated the search for sustainable nutritional alternatives that support growth performance and intestinal health of poultry. Postbiotics and their bioactive metabolites derived from probiotic microorganisms have emerged as promising candidates due to their functional stability and immunometabolic regulatory potential. This study evaluated the effects of Lactobacillus acidophilus-derived postbiotics on growth performance, nutrient sensing, intestinal barrier integrity, immune response, antioxidant status, and gut microbiota in broiler chickens. For this purpose, a total of 400 day-old broilers were randomly assigned to four dietary treatments with graded postbiotic supplementation (0.0%, 0.5%, 1.0%, and 2.0%) for 42 days. Growth performance, immune and antioxidant indices, intestinal and hepatic histomorphology, gene expression, and cecal microbial composition were assessed. Broilers receiving 1.0% and 2.0% postbiotics exhibited significantly higher average daily gain and feed intake compared with controls (p < 0.05). Postbiotic supplementation enhanced systemic immunity, reflected by increased serum IgA, IgG, and IgM levels and elevated spleen and bursa indices. Improved intestinal morphology was evidenced by increased duodenal villus height and villus height-to-crypt depth ratio, while hepatic tissues showed reduced inflammation and fibrosis. Molecular analyzes revealed upregulation of nutrient transporters (SGLT1, PepT1), tight junction protein ZO-1, and antioxidant enzyme GPX1, alongside downregulation of pro-inflammatory cytokines (IL-1β and IL-6). Additionally, postbiotics increased the abundance of beneficial cecal taxa, including coliforms, Lactobacillus, and total plate count. Collectively, L. acidophilus-derived postbiotics improve broiler performance by coordinating nutrient transporter regulation, antioxidant signaling, and inflammatory control, supporting their application as a sustainable AGPs alternative.

IgA nephropathy (IgAN) is the most common primary glomerulonephritis worldwide. A Proliferation-Inducing Ligand (APRIL) plays a critical role in the development and progression of IgAN. This study aimed to evaluate the efficacy and safety of sibeprenlimab, an APRIL receptor antagonist, in IgAN patients. A comprehensive literature search was conducted in PubMed, Embase, Web of Science, and Cochrane Library from database inception to November 30, 2025. Randomized controlled trials (RCTs) were identified. Literature quality was assessed using the Cochrane Risk of Bias 2 tool. Data were analyzed using RevMan 5.4. Two high-quality, multi-center, double-blinded RCTs involving 665 primary IgAN patients were included. Compared with the control group, the sibeprenlimab group showed a greater percentage reduction in urine protein-to-creatinine ratio (UPCR) (MD -48.35, 95% CI -62.00 to -34.69, P < 0.00001), a lower proportion of patients experiencing hematuria (OR 0.11, 95% CI 0.06 to 0.20, P < 0.00001), a lower least-squares mean change in estimated glomerular filtration rate (eGFR) (MD 6.11, 95% CI 2.06 to 10.16, P = 0.003), and a marked decrease in circulating galactose-deficient IgA1 (Gd-IgA1) and serum APRIL levels (mean reductions of 66.0% and 95.8%, respectively). Although the overall incidence of adverse events was comparable (OR 0.90, 95% CI 0.39 to 2.09, P = 0.80), the sibeprenlimab group experienced a greater reduction in serum IgG, IgA, and IgM levels than the control group (mean reductions of 35.0%, 66.5%, and 74.8%, respectively). Current limited but robust evidence suggests that sibeprenlimab is effective in reducing proteinuria and hematuria, lowering circulating Gd-IgA1 and serum APRIL levels, and slowing the decline in eGFR in IgAN patients. Although sibeprenlimab exhibits an overall favorable safety profile, it may be associated with reductions in serum IgG, IgA, and IgM levels. Not applicable.

Plasmodium vivax is responsible for most malaria cases in Latin America and Southeast Asia and can cause severe manifestations. Prevention strategies such as vaccines, have been hampered by the complexity of the parasite's life cycle, especially in the liver stages. The P. vivax-Liver-Specific Protein 2 (Pv_LISP-2) has been described as essential for intrahepatic development, but its antigenicity has not yet been explored. Thus, in this study we evaluate the naturally acquired humoral response against two regions of Pv_LISP-2 in populations from the Brazilian Amazon exposed to P. vivax infection. Plasma samples were collected from infected individuals in Manaus (Amazonas state) and Boa Vista (Roraima state). Two structural regions of Pv_LISP-2 (Pv_L.seq1 and Pv_L.seq2) were expressed in E. coli, purified, and applied in ELISA assays to detect total IgM, IgG, and IgG subclasses antibodies. Furthermore, longitudinal follow-up was conducted for up to 180 days in part of the Manaus cohort. Pv_LISP-2 fragments were recognized by antibodies of P. vivax-infected individuals. During the acute phase, the response was characterized by high levels of IgM, followed by the induction of IgG, especially against Pv_L.seq1. The cytophilic subclasses IgG1 and IgG3 were the predominant subclasses. IgM responses correlated with parasitemia and days of symptoms but showed a negative association with hematological parameters (hemoglobin, hematocrit, and erythrocytes). This is the first study to evaluate naturally acquired antibodies against this liver-stage antigen of P. vivax, we showed that Pv_LISP-2 is naturally antigenic in individuals exposed to vivax malaria. While the functional implications of these responses remain to be fully elucidated, our findings support further investigation of Pv_LISP-2 as a potential vaccine candidate targeting the liver stage of P. vivax.

Severe infections contribute to morbidity and mortality in microscopic polyangiitis (MPA). This study aims to investigate the clinical characteristics and identify risk factors for early severe infections in newly diagnosed patients with MPA. This retrospective cohort study included patients newly diagnosed with MPA followed up for at least 6 months at two tertiary care centres between January 2013 and December 2023. Clinical data, including demographics, laboratory findings, treatment regimens, and infection details, were collected. Multivariable logistic regression analysis was used to identify risk factors for severe infections within 6 months after the diagnosis in patients with new-onset MPA. A total of 374 patients with MPA were included, and 25.9% (97/374) experienced severe infections. Compared to the non-infection group, the infection group had a significantly higher daily average dosage of prednisone for remission induction, a higher proportion of patients with a history of chronic lung disease, and a higher proportion receiving rituximab (RTX) therapy (p<0.05). In multivariable logistic regression analysis, a history of chronic lung disease, higher daily average dosage of prednisone therapy and RTX therapy for remission induction were associated with an increased risk of severe infections, whereby higher baseline serum IgM levels were associated with a decreased risk. The most common site of infection was the lung (75.23%), and bacteria (43.1%) was the most prevalent pathogen. MPA is associated with a high risk of severe infections, especially in patients treated with higher dosage glucocorticoid and with a history of chronic lung disease.

Background: Selective immunoglobulin A deficiency (sIgAD), the most common primary immunodeficiency, is associated with recurrent respiratory infections. Despite the established role of IgA in mucosal immunity, population-based data evaluating COVID-19 susceptibility and severity among individuals with sIgAD are scarce. Objectives: This study aimed to evaluate the association between selective IgA deficiency and the risk of SARS-CoV-2 infection, recurrent infection, COVID-19-related hospitalization, and vaccination uptake. Design and Setting: We conducted a retrospective population-based cohort study using the Clalit Health Services electronic health record database in Israel. Methods: Adults aged ≥18 years with documented serum IgA measurements between 2020 and 2022 were included. Selective IgA deficiency was defined as serum IgA < 7 mg/dL with normal IgG and IgM levels. Individuals with sIgAD were matched 1:4 with controls with normal IgA levels by age and sex. Outcomes included documented SARS-CoV-2 infection, recurrent infection (>2 episodes), COVID-19-related hospitalization, and vaccination status. Multivariable logistic regression models were adjusted for demographic characteristics, comorbidities, and vaccination status. Results: The matched cohort included 61,150 individuals (12,230 with sIgAD and 48,920 controls). The risk of primary SARS-CoV-2 infection did not differ significantly between groups (13.0% vs. 14.0%; adjusted OR 1.03, 95% CI 0.95-1.12). However, individuals with sIgAD had increased odds of recurrent infection (adjusted OR 1.15, 95% CI 1.09-1.22) and COVID-19-related hospitalization (adjusted OR 1.40, 95% CI 1.22-1.60). Booster vaccination uptake was slightly higher among individuals with sIgAD. Conclusions: Selective IgA deficiency was not associated with increased susceptibility to primary SARS-CoV-2 infection but was independently associated with recurrent infection and increased risk of hospitalization. These findings underscore the importance of mucosal immunity in post-infection viral control and suggest that individuals with sIgAD may benefit from closer monitoring after COVID-19 infection.