The Vitamin D Status in Children With Newly Diagnosed Acute Lymphoblastic Leukemia and Its Potential Impact on the Primary Symptoms of Leukemia and Course of Induction Treatment.

BACKGROUND: Vitamin D deficiency is ubiquitous within the population of children. A similar problem is recognized among pediatric patients with acute lymphoblastic leukemia. The purpose of this study was to analyze the prevalence of vitamin D deficiency and to investigate the connection between vitamin D status and the course of induction treatment of ALL. MATERIALS AND METHODS: A cross-sectional study including 59 patients with newly diagnosed ALL from May 2017 until November 2020. RESULTS: Vitamin D deficiency was found in 39% of the patients. There were no seasonal differences in vitamin D status. Patients with optimal 25(OH)D concentration presented more profound thrombocytopenia ( P =0.015) and required more frequent platelet transfusions ( P =0.018). Good prognosis factors such as B phenotype and hyperdiploidy were also more frequent among children with higher 25(OH)D concentration ( P =0.01 and 0.014, respectively). CONCLUSIONS: The study showed that patients with a higher serum concentration of 25(OH)D presented deeper thrombocytopenia and needed more frequent transfusions. Moreover, those patients showed higher rates of B-cell leukemia and hyperdiploid karyotype. We did not find any influence of the possible exposure to sunlight (defined as the season of the year on admission) on serum 25(OH)D concentration, which supports the argument for supplementing vitamin D all year round. Moreover, the supplementing of vitamin D seems to be safe and does not cause any renal complications connected to calcium and phosphorus imbalance as no correlation between their levels and 25(OH)D concentration was found.

Polish recommendations for diagnosis and therapy of paediatric stroke.

Stroke remains one of the greatest health challenges worldwide, due to a high mortality rate and, despite great progress in its treatment, the significant disability that it causes. Studies conducted around the world show that the diagnosis of stroke in children is often significantly delayed. Paediatric ischaemic arterial stroke (PAIS) is not only a problem that varies greatly in frequency compared to the adult population, it is also completely different in terms of its risk factors, clinical course and outcome. The main reason for the lack of a rapid diagnosis of PAIS is a lack of access to neuroimaging under general anaesthesia. The insufficient knowledge regarding PAIS in society as a whole is also of great importance. Parents and carers of children should always bear in mind that paediatric age is not a factor that excludes a diagnosis of stroke. The aim of this article was to develop recommendations for the management of children with acute neurological symptoms suspected of ischaemic stroke and further treatment after confirmation of the ischaemic aetiology of the problem. These recommendations are based on current global recommendations for the management of children with stroke, but our goal was also to match them as closely as possible to the needs and technical diagnostic and therapeutic possibilities encountered in Poland. Due to the multifactorial problem of stroke in children, not only paediatric neurologists but also a neurologist, a paediatric cardiologist, a paediatric haematologist and a radiologist took part in the preparation of these recommendations.

Hematopoietic stem cell transplantation in a patient with activated phosphoinositide 3-kinase δ syndrome: A case report and literature review.

Activated phosphoinositide 3-kinase δ syndrome (APDS) is a recently described disease characterized by recurrent infections, lymphoproliferation with a high risk of malignancy, early-onset cytopenia, and a propensity for autoimmune diseases. Hematopoietic stem cell transplantation (HSCT) has proven to be an effective treatment method; however, the recovery process after HSCT is prolonged and accompanied by complications. In this study, we present the case of a patient with APDS type 1. Despite showing signs of immunodeficiency at the age of 6 months, it took almost 6 years to reach a definitive diagnosis. The patient experienced recurrent infections, often accompanied by anemia requiring transfusions, and multifocal nonmalignant lymphoproliferation. Only after receiving the appropriate diagnosis was it possible to implement proper and accurate treatment. HSCT was performed when the patient was 6 years old, leading to significant improvement in his condition. At the 17-month post-HSCT follow-up, the boy is asymptomatic and in good general health, although close monitoring continues due to mixed chimerism and delayed humoral immune recovery. Applying HSCT before the patient develops malignancy contributes to expanding the use of HSCT as a treatment option for APDS type 1.

Characteristics and treatment results of refractory and relapsed acute myeloid leukaemia in paediatric patients treated in Polish Paediatric Leukaemia/Lymphoma Study Group institutions according to the Protocol Acute Myeloid Leukaemia Berlin-Frankfurt-Munster 2012 and a review of novel treatment possibilities in paediatric acute myeloid leukaemia.

Introduction: This study aimed to present the clinical features and results of treatment of patients diagnosed with refractory or relapsed acute myeloid leukaemia (AML) in Polish Paediatric Leukaemia/Lymphoma Study Group (PPL/LSG) institutions, treated in accordance with the Protocol Acute Myeloid Leukaemia Berlin-Frankfurt-Munster 2012, as their first-line therapy. Material and methods: The outcome data of 10 patients with refractory AML (median age 9.5 years) and 30 with relapsed AML (median age 12 years) were analysed retrospectively. Re-induction was usually based on idarubicin, fludarabine, and cytarabine along with allogeneic haematopoietic stem cell transplant (allo-HSCT) in 5 patients with refractory AML and 7 relapsed AML children. Results: 37.5% (3/8) of refractory AML patients achieved second complete remission second complete remission (CRII). One of ten patients (1/10; 10%) was alive and stayed in complete remission for 34 months after the allo-HSCT. The probability of 3-year event-free survival (pEFS) in this group was 0.125 ±0.11. In the group of relapsed AML patients, the CRII was achieved in 9 patients (34%), and the probability of survival was: pEFS = 0.24 ±0.08; probability overall survival (pOS) = 0.34 ±0.09, with significantly better results achieved in patients who underwent allo-HSCT (pOS = 0.54 ±0.14 vs. 0.08 ±0.08, p < 0.0001). Conclusions: The prognosis of refractory AML and the first AML recurrence in children who were first-line treated in PPL/LSG centres according to Protocol Acute Myeloid Leukaemia Berlin-Frankfurt-Munster 2012 is poor. Failures of re-induction treatment particularly result from difficulties in achieving remission. Allogeneic HSCT improves prognosis in children with refractory and first recurrent AML, under the condition it is performed in complete remission. Novel therapeutic approaches are needed to increase the remission rate and improve the outcomes.

COVID-19-related Gastrointestinal Bleeding in a Pediatric Patient With ALL.

Coronavirus disease 2019 (COVID-19) is a contagious disease caused by severe acute respiratory syndrome coronavirus-2. Patients with hematologic malignancies have been shown to have higher risk of mortality due to COVID-19 than reported in the general adult population. Reports on acute lymphoblastic leukemia and COVID in children are scarce. We present a case of an 11-year-old male patient undergoing treatment for B-cell acute lymphoblastic leukemia with an atypical course of COVID-19. The patient received a positive result of the syndrome coronavirus-2 polymerase chain reaction test performed due to epidemiologic reasons. The chemotherapy was continued since the patient had no clinical signs of COVID-19. The disease started with intensive gastrointestinal bleeding, followed by severe respiratory tract infection over 2 weeks later.

Photobiomodulation Treatment in Chemotherapy-Induced Oral Mucositis in Young Haematological Patients-A Pilot Study.

Background and Objectives: One of the most debilitating side effects of chemotherapy is oral mucositis (OM). Photobiomodulation (PBM) demonstrates high efficacy in the management of OM. The aim of the study was to investigate the incidence of oral mucositis and evaluation of the effectiveness of PBM therapy. Materials and Methods: A total of 23 children diagnosed with leukaemia or lymphoma affected by chemotherapy-induced OM were enrolled in the study. OM grade was assessed with the World Health Organization (WHO) scale. Patients completed an approved questionnaire, and blood cell counts were read every 2 days. OM lesions were treated with class IV laser therapy with a frequency of every 48 h and density of 2, 4, 8, 16 or 30 J/cm2. The level of pain was measured with VAS scale. Results: The 23 patients developed a total of 41 OM episodes with a mean duration of 7.61 days ± 4.70. Laser therapy showed a great reduction regarding pain and a better function of patients even with neutropenia. Conclusions: Oral mucositis represents a significant burden to children. PBM brings positive aspects for patients; however, the optimal treatment parameters require further study.

Childhood Sjögren syndrome: features of an international cohort and application of the 2016 ACR/EULAR classification criteria.

OBJECTIVE: Sjögren syndrome in children is a poorly understood autoimmune disease. We aimed to describe the clinical and diagnostic features of children diagnosed with Sjögren syndrome and explore how the 2016 ACR/EULAR classification criteria apply to this population. METHODS: An international workgroup retrospectively collected cases of Sjögren syndrome diagnosed under 18 years of age from 23 centres across eight nations. We analysed patterns of symptoms, diagnostic workup, and applied the 2016 ACR/EULAR classification criteria. RESULTS: We identified 300 children with Sjögren syndrome. The majority of patients n = 232 (77%) did not meet 2016 ACR/EULAR classification criteria, but n = 110 (37%) did not have sufficient testing done to even possibly achieve the score necessary to meet criteria. Even among those children with all criteria items tested, only 36% met criteria. The most common non-sicca symptoms were arthralgia [n = 161 (54%)] and parotitis [n = 140 (47%)] with parotitis inversely correlating with age. CONCLUSION: Sjögren syndrome in children can present at any age. Recurrent or persistent parotitis and arthralgias are common symptoms that should prompt clinicians to consider the possibility of Sjögren syndrome. The majority of children diagnosed with Sjögren syndromes did not meet 2016 ACR/EULAR classification criteria. Comprehensive diagnostic testing from the 2016 ACR/EULAR criteria are not universally performed. This may lead to under-recognition and emphasizes a need for further research including creation of paediatric-specific classification criteria.

Molecular Background, Clinical Features and Management of Pediatric Mastocytosis: Status 2021.

Pediatric mastocytosis is a heterogeneous disease characterized by accumulation of mast cells in the skin and less frequently in other organs. Somatic or germline mutations in the KIT proto-oncogene are detected in most patients. Cutaneous mastocytosis is the most common form of the disease in children. In the majority of cases, skin lesions regress spontaneously around puberty. However, in few patients, mastocytosis is not a self-limiting disease, but persists into adulthood and can show signs of systemic involvement, especially when skin lesions are small-sized and monomorphic. Children with mastocytosis often suffer from mast cell mediator-related symptoms. Severe hypersensitivity reactions can also occur, mostly in patients with extensive skin lesions and blistering. In a substantial number of these cases, the triggering factor of anaphylaxis remains unidentified. Management of pediatric mastocytosis is mainly based on strict avoidance of triggers, treatment with H1 and H2 histamine receptor blockers, and equipment of patients and their families with epinephrine auto-injectors for use in severe anaphylactic reactions. Advanced systemic mastocytosis occurs occasionally. All children with mastocytosis require follow-up examinations. A bone marrow investigation is performed when advanced systemic mastocytosis is suspected and has an impact on therapy or when cutaneous disease persists into adulthood.

Varicella-zoster virus infection in the pediatric population with acute lymphoblastic leukemia in Poland.

Varicella-zoster virus (VZV) infection in pediatric hemato-oncology patients can be a therapeutic problem when children are exposed to immunosuppression. The aim of this study is to evaluate the incidence of VZV infection, antiviral therapy and outcome in children with ALL treated in polish hemato-oncological centers between 2012 and 2019 years. This study included medical records of 1874 patients, aged 1 to 18 years, with newly diagnosed acute lymphoblastic leukemia. During chemotherapy, 406 children out of 1874 (21.6%) experienced viral infections. The incidence of VZV infection in the whole group children with ALL was 1.8%. Among them, 34 (8.4%) patients were diagnosed with VZV infection. Thirty-five episodes of viral infections were identified. The median time of VCV therapy was 12 days. Herpes zoster infection occurred in 24 (70.6%) children, and varicella in 10 (29.4%) ones. The average time from the start of chemotherapy to the appearance of herpes zoster was 7.26 ± 4.05 months. VZV infection occurred mainly during the maintenance therapy, the reinduction and induction phases. There was no correlation between steroid dosage or type and subsequent zoster. The total lymphocyte count of these patients on the first day of zoster was reduced. No serious complications were observed due to this infection. All patients survived. In conclusion, a low incidence of VZV infection was observed among pediatric patients with ALL in Poland. This analysis indicates that currently used therapeutic methods are effective in children with cancer and VZV infection. The main focus should be on the prevention of delayed chemotherapy.

Mixed phenotype acute leukemia: Biological profile, clinical characteristic and treatment outcomes: Report of the population-based study.

OBJECTIVES: The aim of this population-based, retrospective study was to analyze biological and clinical features and treatment results in children diagnosed with MPAL in all Polish pediatric oncology centers between 2007 and 2018. METHODS: Among 2893 children and adolescents diagnosed and treated for acute leukemia, 39 (1.35%) patients fulfilled the WHO criteria of MPAL. The T/myeloid phenotype was most prevalent. RESULTS: Cytogenetics findings were seen in 2 (5.1%), while chromosomal abnormalities were found in 14 (35.9%) patients. Thirty-two patients achieved CR-1, including 23 (92.0%) treated with ALL-directed chemotherapy and 9 (64.3%) treated with AML-type induction regimens. Within these patients, 4 (12.5%) died due to treatment-related complications and 11 (34.4%) relapsed. Nineteen (63.3%) patients underwent allo-HSCT in CR-1 and 14 (73.7%) of them have been in CR-1. In total, 17 (43.6%) patients remain in CR-1 for 1-12 years, including 14 (58.3%) with T/myeloid MPAL. The 5-year pOS and pEFS were 51.8% and 44.2%, respectively. The overall survival for ALL-directed therapy was significantly better than the one for AML-type chemotherapy (P = .001). It was also better for patients who underwent HSCT in CR-1 (P = .001). CONCLUSIONS: The prognosis of MPAL is unsatisfactory, but initial treatment with ALL-directed chemotherapy consolidated with allo-HSCT improves the outcomes in MPAL.

Infectious profile in children with ALL during chemotherapy: A report of study group for infections.

INTRODUCTION: The treatment-related mortality in currently published studies of acute lymphoblastic leukemia (ALL) in children is 2-4%, mainly due to infections. The aim of the study was to analyse the incidence, epidemiology, profile of infection and the death rate in children with ALL. PATIENTS AND METHODS: The retrospective analysis included 1363 patients, aged 1-18 years, with newly diagnosed ALL, who were treated in 17 pediatric hematology centers between 2012 and 2017 in Poland. The patients received therapy according to the ALL IC-BFM 2002 and 2009 (International Berlin-Frankfurt-Munster Study Group) protocols. RESULTS: In our study, 726 out of 1363 (53.2%) children were reported to have a microbiologically documented bacterial infection during chemotherapy. 1511 episodes of these infection were diagnosed. A total number of 251/1363 (18.4%) children experienced a viral infection. 304 episodes were documented by PCR test (polymerase chain reaction). A fungal infection was reported in 278 (20.4%) children, including 10.1% of probable, 6.0% of proven, 83% of possible diagnosis. A higher frequency of fungal infection was noted in the recent years. In our material, the rate of death was 2.4%, mainly due to fungal infection. CONCLUSIONS: Our results present the epidemiology of infectious disease in the Polish ALL patient population. The most frequent were bacterial infections, followed by fungal and viral ones. Similar to the previously published data, the mortality rate in our material was 2.4%.

Epidemiology and outcome of invasive fungal disease in children after hematopoietic cell transplantation or treated for malignancy: Impact of national programme of antifungal prophylaxis.

The objective of the study was the analysis of incidence and outcome of invasive fungal disease (IFD) in children treated for malignancy (PHO, paediatric hematology-oncology) or undergoing hematopoietic cell transplantation (HCT) over a period of six consecutive years in nationwide study. A total number of 5628 patients with newly diagnosed malignancies and 971 patients after HCT (741 allo-HCT and 230 auto-HCT) were screened for infectious complications in biennial reports. IFD incidence was lower among PHO patients: 8.8% vs 21.2% (P < .0001) and survival from IFD was better: 94.2% vs 84.1% (P < .0001). Auto-HCT patients had lower incidence (10.9% vs 24.4%) and lower mortality than allo-HCT patients. Introduction of national antifungal prophylaxis programme in HCT and acute leukaemia patients decreased incidence of IFD in HCT (from 23.1% to 13.4%) and AML on conventional chemotherapy (from 36% to 23%) but not in ALL patients during chemotherapy. In multivariate analysis, the incidence of IFD was higher in patients after HCT, diagnosed for ALL, AML or NHL, and in patients > 10 years old. Factors contributing to death with infection were as follows: undergoing HCT, diagnosis of acute leukaemia (ALL or AML) and duration of treatment of infection > 21 days. In conclusion, the incidence of IFD in allo-HCT and in AML patients on chemotherapy has decreased after introduction of national programme of antifungal prophylaxis, while the incidence of IFD in ALL patients on chemotherapy did not change significantly. The outcome of IFD both in PHO and HCT patients has largely improved in comparison with historical international data.

Isavuconazole in a Successful Combination Treatment of Disseminated Mucormycosis in a Child with Acute Lymphoblastic Leukaemia and Generalized Haemochromatosis: A Case Report and Review of the Literature.

Invasive mucormycosis in immunocompromised children is a life-threatening fungal infection. We report a case of a 7-year-old girl treated for acute lymphoblastic leukaemia complicated by disseminated mucormycosis during induction therapy. Microscopic examination of surgically removed lung tissue revealed wide, pauci-septate hyphae suggesting a Mucorales infection. This diagnosis was confirmed immunohistochemically and by PCR analysis followed by a final identification of Cunninghamella sp. The patient was treated successfully with surgical debridement and antifungal combination therapy with amphotericin B, caspofungin and isavuconazole. The use of isavuconazole in a child was not previously reported. Additionally, case reports concerning pulmonary mucormycoses in paediatric population published after 2010 were reviewed. Nineteen out of 26 identified patients suffered from haematological diseases. Reported mortality reached 38.5%. By the fact of rising morbidity, unsatisfactory results of treatment and remaining high mortality of mucormycoses in immunocompromised patients, new therapeutic options are warrant. Isavuconazole, with its broad-spectrum activity, good safety profile and favourable pharmacokinetics, is a promising drug. However, further studies are necessary to confirm positive impact of isavuconazole on mucormycosis treatment in children.

Sinusoidal obstruction syndrome in a paediatric patient with acute lymphoblastic leukaemia after completion of reinduction therapy according to ALL Intercontinental Berlin-Frankfurt-Münster 2009.

Sinusoidal obstruction syndrome (SOS), also termed veno-occlusive disease (VOD) of the liver, is a well-known complication of haematopoietic stem cell transplantation (HSCT) both in children and adults. In the medical literature there are occasional reports of SOS in patients receiving conventional chemotherapy. In children with solid tumours this entity occurs during treatment of nephroblastoma, rhabdomyosarcoma, and medulloblastoma. In the late 1990s SOS was quite often observed as the complication of oral 6-thioguanine (6-TG) in patients suffering from acute lymphoblastic leukaemia (ALL), who received 6-TG throughout maintenance. In current protocols, the syndrome has become uncommon because treatment with 6-TG is limited to two weeks of oral therapy. Here, we report a case of a nine-year-old boy with ALL, who developed sinusoidal obstruction syndrome shortly after completing the reinduction block of chemotherapy (cyclophosphamide, cytarabine, thioguanine) according to the ALL Intercontinental Berlin-Frankfurt-Münster 2009 (ALL IC BFM 2009) treatment protocol.

Fournier Gangrene Caused by Candida albicans in an Infant After Cardiac Surgery.

Fournier gangrene is a rare, rapidly progressive, life-threatening condition. We report a 23-day-old boy with pulmonary atresia and ventricular septal defect treated surgically, who developed Fournier gangrene. Emergency surgery was performed with tissue sampling for microbiological examination. Candida albicans was confirmed; caspofungin followed by fluconazole was administered with excellent results.

Managing Undernutrition in Pediatric Oncology: A Consensus Statement Developed Using the Delphi Method by the Polish Society for Clinical Nutrition of Children and the Polish Society of Pediatric Oncology and Hematology.

"Managing Undernutrition in Pediatric Oncology" is a collaborative consensus statement of the Polish Society for Clinical Nutrition of Children and the Polish Society of Pediatric Oncology and Hematology. The early identification and accurate management of malnutrition in children receiving anticancer treatment are crucial components to integrate into comprehensive medical care. Given the scarcity of high-quality literature on this topic, a consensus statement process was chosen over other approaches, such as guidelines, to provide comprehensive recommendations. Nevertheless, an extensive literature review using the PubMed database was conducted. The following terms, namely pediatric, childhood, cancer, pediatric oncology, malnutrition, undernutrition, refeeding syndrome, nutritional support, and nutrition, were used. The consensus was reached through the Delphi method. Comprehensive recommendations aim to identify malnutrition early in children with cancer and optimize nutritional interventions in this group. The statement underscores the importance of baseline and ongoing assessments of nutritional status and the identification of the risk factors for malnutrition development, and it presents tools that can be used to achieve these goals. This consensus statement establishes a standardized approach to nutritional support, aiming to optimize outcomes in pediatric cancer patients.

Acute Pancreatitis in Pediatric Acute Lymphoblastic Leukemia (AcuPA Study): A Nationwide Survey in Poland.

PURPOSE: This study aimed to identify the risk factors for acute pancreatitis (AP) and its impact on outcomes in Polish children treated for ALL. METHODS: The study group included 2303 children receiving intensive chemotherapy for ALL. The group was divided into patients with at least one episode of AP and those who did not develop AP after treatment for ALL. RESULTS: The cumulative incidence of AP in the study group was 4.08%. Older age was an independent risk factor for the development of AP (OR = 1.05; 95%CI = 1.006-1.098; p = 0.03). The overall mortality associated with AP was 2.13%. The probabilities of disease-free survival (p-DFS) and event-free survival (p-EFS) in both subgroups were 0.84 vs. 0.86, log-rank p = 0.65 and 0.75 vs. 0.80, log-rank p = 0.12, respectively. A total of 22 out of 94 patients (23.4%) with AP were re-exposed to asparaginase (ASP) during the subsequent treatment phases. Only one patient re-exposed to ASP (4.5%) developed a second episode of AP. There were no significant differences in p-DFS and p-EFS between patients re-exposed and not re-exposed to asparaginase (0.78 vs. 0.86, log-rank p = 0.27 and 0.63 vs. 0.79, log-rank p = 0.09, respectively). CONCLUSIONS: The incidence of AP in children with ALL is low and related to patients' age. The development of AP does not seem to influence p-DFS and p-EFS in children with ALL. Recurrence of AP after re-exposure to asparaginase in patients with ALL and a history of AP is low (4.5%). Re-exposure to asparaginase after the first episode of AP does not improve either p-DFS or p-EFS in children with ALL.

Anti-PD-1 Therapy in Advanced Pediatric Malignancies in Nationwide Study: Good Outcome in Skin Melanoma and Hodgkin Lymphoma.

BACKGROUND/AIM: The role of immune checkpoint inhibitors (ICIs; anti-PD1) in the treatment of childhood cancers is still evolving. The aim of this nationwide retrospective study was to assess the safety and effectiveness of ICIs used in a group of 42 patients, with a median age of 13.6 years, with various types of advanced malignancies treated in pediatric oncology centers in Poland between 2015 and 2023. RESULTS: The indications for treatment with anti-PD1 were as follows: Hodgkin lymphoma (11); malignant skin melanoma (9); neuroblastoma (8); and other malignancies (14). At the end of follow-up, complete remission (CR) was observed in 37.7% (15/42) of children and disease stabilization in 9.5% (4/42), with a mean survival 3.6 (95% CI = 2.6-4.6) years. The best survival (OS = 1.0) was observed in the group of patients with Hodgkin lymphoma. For malignant melanoma of the skin, neuroblastoma, and other rare malignancies, the estimated 3-year OS values were, respectively, 0.78, 0.33, and 0.25 (p = 0.002). The best progression-free survival value (0.78) was observed in the group with malignant melanoma. Significantly better effects of immunotherapy were confirmed in patients ≥ 14 years of age and good overall performance ECOG status. Severe adverse events were observed in 30.9% (13/42) patients.

Pre-Exposure Prophylaxis and Treatment with Tixagevimab/Cilgavimab for COVID-19 among Immunocompromised Pediatric Patients.

Background: Patients treated with hemato-oncological malignancies (HO) or undergoing cellular therapies such as hematopoietic stem cell transplantation (HSCT) or chimeric antigen receptor T cells (CAR-T) were significantly affected by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Despite the success of SARS-CoV-2 vaccination, immunocompromised patients remain at increased risk for severe coronavirus disease (COVID-19), rendering this group of population a high priority for additional prevention and treatment options. Tixagevimab and Cilgavimab (TIXA/CILGA, AZD7442, Evusheld®) is a combination of two fully human, long-acting monoclonal antibodies. TIXA/CILGA have been approved as pre-exposure prophylaxis and treatment in patients at risk of severe disease with impaired vaccine response. Our objective was to describe the efficacy and safety among immunocompromised pediatric patients. Methods: This was an observational multicenter cohort study of immunocompromised pediatric patients receiving TIXA/CILGA conducted at nine Polish centers of Pediatric Oncology, Hematology and Bone Marrow Transplantation. We analyzed patients in two groups; those treated with HO and those undergoing cellular therapies: HSCT or CAR-T cells. In addition, two other cohorts were identified: patients given TIXA/CILGA as pre-exposure prophylactic and therapeutic intervention. Results: A total of 78 patients were evaluated during the study period: 69 (88.5%) received TIXA/CILGA as pre-exposure prophylaxis and 9 (11.5%) as a treatment strategy. A total of 52 (66.6%) patients were treated with standard chemotherapy at HO departments; 21 (27%) underwent HSCT, and 5 (6.4%) received CAR-T cell therapy. All children with COVID-19 receiving TIXA/CILGA presented a mild degree of severity. The most common clinical manifestations were fever, cough and coryza. At least one adverse event (AE) was reported in two (3.8%) patients excluding standard injection site reactions. Reported AEs were mild or moderate in intensity. One child reported mild myalgia and one reported moderate bone pain and weakness. Conclusions: In our observational multicenter cohort study, we explored the use of TIXA/CILGA as pre-exposure prophylaxis and treatment for COVID-19 among immunocompromised pediatric patients. While our findings suggest a potential benefit in preventing and managing COVID-19 in this vulnerable population, it is important to note the study's non-comparative design. Our results highlight the need for well-designed clinical trials to confirm these observations and further assess the efficacy and safety of TIXA/CILGA in immunocompromised children.