Objective: Data on the risk factors, outcomes, and long-term effects of SARS-CoV-2 infection (COVID-19), especially following hematopoietic stem cell transplantation (HSCT) in pediatric patients with inborn errors of immunity (IEI) are limited. The study aims to define the clinical course of infection and identify risk factors for a worse outcome and long-term effects of COVID-19 in individuals with IEIs and those who have received HSCT for IEIs.

Materials and Methods: In this single-center analysis, we retrospectively analyzed 74 pediatric IEI patients with COVID-19 between March 2020 and March 2023. Sixty-four patients were evaluated about COVID-19`s long-term consequences one year after the outbreak.

Results: Most patients exhibited combined immunodeficiency (51%), followed by antibody deficiency (28%), and syndromic combined immunodeficiencies (12%). Two patients had liver transplants, and 27 patients had HSCT before COVID-19. Thirty-two patients (43%) were hospitalized, and 3 (4%) died. The median time from HSCT to COVID-19 infection was 59 months (min 16 days, max 192 months). The major risk factor for infection severity was chronic pulmonary illness. Severe COVID-19 was associated with musculoskeletal abnormalities (p < 0.001), chronic lung disease (p < 0.01), hypogammaglobulinemia (p < 0.001), as well as fever and dyspnea (p < 0.01). Higher severity was also linked to the use of immunoglobulin and chemoprophylaxis (both p < 0.001). Mortality was significantly higher in patients with autoinflammatory syndromes and innate immune defects (p < 0.05). There is no difference between post-HSCT patients and our IEI cohort for COVID-19 illness severity. Remdesivir and convalescent plasma were given to five reinfected-relapsing patients. In total, 28 long-term side effects were identified, with fatigue, hair loss, and red eye being the most common.

Conclusion: Overall, we found that hypogammaglobulinemia, chronic lung disease, and musculoskeletal abnormalities are associated with a severe disease course. The clinical course and outcomes of post-HSCT pediatric patients with COVID-19 are generally favourable. The long-term effects of COVID-19 can be seen in both groups regardless of the clinical severity of the disease.