Prevention of infections is crucial in solid organ transplant (SOT) candidates and recipients. These patients are exposed to an increased infectious risk due to previous organ insufficiency and to pharmacologic immunosuppression. Besides infectious-related morbidity and mortality, this vulnerable group of patients is also exposed to the risk of acute decompensation and organ rejection or failure in the pre- and post-transplant period, respectively, since antimicrobial treatments are less effective than in the immunocompetent patients. Vaccination represents a major preventive measure against specific infectious risks in this population but as responses to vaccines are reduced, especially in the early post-transplant period or after treatment for rejection, an optimal vaccination status should be obtained prior to transplantation whenever possible. This review reports the currently available data on the indications and protocols of vaccination in SOT adult candidates and recipients.

Infection is a serious concern in the short and long term after pediatric liver transplantation. Vaccination represents an easy and cheap opportunity to reduce morbidity and mortality due to vaccine-preventable infection. This retrospective, observational, multi-center study examines the immunization status in pediatric liver transplant candidates at the time of transplantation and compares it to a control group of children with acute liver disease. Findings show only 80% were vaccinated age-appropriately, defined as having received the recommended number of vaccination doses for their age prior to transplantation; for DTP-PV-Hib, less than 75% for Hepatitis B and two-thirds for pneumococcal conjugate vaccine in children with chronic liver disease. Vaccination coverage for live vaccines is better compared to the acute control group with 81% versus 62% for measles, mumps and rubella (p = 0.003) and 65% versus 55% for varicella (p = 0.171). Nevertheless, a country-specific comparison with national reference data suggests a lower vaccination coverage in children with chronic liver disease. Our study reveals an under-vaccination in this high-risk group prior to transplantation and underlines the need to improve vaccination.

Solid organ transplant (SOT) candidates and recipients are a fragile population, in which the presence of a pre-transplant disease leading to organ insufficiency and the post-transplant immunosuppressive treatment expose them to an increased risk of infectious diseases. The best intervention to guarantee efficient prevention of infections, with optimal cost–benefit ratio, is represented by vaccination programs; however, the response to vaccines needs that the immune system maintains a good function. This is even more relevant at paediatric age, when specific immunological conditions make transplant candidates and recipients particularly vulnerable. Paediatric patients may be naïve to most infections and may have incomplete immunization status at the time of transplant listing due to their age. Moreover, the unaccomplished development of a mature immune system and the immunosuppressive regimen adopted after transplant might affect the efficacy of post-transplant vaccinations. Therefore, every effort should be made to obtain the widest vaccination coverage before the transplantation, whenever possible. This review reports the most relevant literature, providing information on the current approach to the vaccinations in paediatric SOT candidates and recipients.

Infectious diseases remain a leading cause of morbidity and mortality among pediatric transplant recipients, despite significant advances in transplantation management. Vaccination is the most effective strategy to prevent infections; however, its efficacy is hindered in solid organ transplant (SOT) and hematopoietic stem cell transplant (HSCT) recipients, due to altered immune responses. Pediatric SOT candidates often have incomplete vaccination status prior to transplantation and reduced vaccine efficacy post‐transplant due to immunosuppressive therapy. They are also at greater risk of vaccine‐preventable infections compared to adults, leading to higher rates of hospitalization, graft loss, and death. In HSCT recipients, immune ablation and reconstitution result in the loss of immunologic memory, rendering both pre‐ and post‐transplant vaccine strategies particularly challenging. Factors such as graft‐versus‐host disease, immunoglobulin therapy, and ongoing immunosuppression further complicate timing and effectiveness of vaccinations. Despite established guidelines emphasizing timely immunization, several studies report low vaccination coverage and inadequate protective immunity in both groups. Barriers include intercurrent illness, variation in national immunization schedules, vaccine hesitancy, and uncertainties regarding optimal vaccination timing. In this position statement, the European Reference Network (ERN) TransplantChild Working Group conducted a comprehensive literature review on the most relevant studies on vaccinations in pediatric transplant candidates and recipients, with the aim of developing evidence‐based recommendations tailored to pediatric SOT and HSCT recipients. This position paper outlines current challenges, summarizes existing evidence, and proposes recommendations to improve immunization practices in this high‐risk population.