Publication date: May 19, 2025
Background/Objectives: SARS-CoV-2 infection has the potential to cause multi-organ involvement and, when associated with Epstein-Barr virus (EBV) coinfection, may worsen the course of disease in pediatric patients by influencing the immune response. Methods: Our retrospective-observational study included 406 hospitalized children with post-COVID-19 status or SARS-CoV-2/EBV coinfection. Results: Hypovitaminosis D was more common in the coinfected sublot (59. 18%) than in the COVID-19 one (50. 74%), with a higher frequency of severe vitamin D deficiency (16. 33% vs. 7. 35%). Hypovitaminosis D was significantly associated with female sex (p = 0. 033) only in the COVID-19 subgroup. Hypervitaminosis D, although rare, was only associated with severe forms of the disease (7. 69%). Between clinical severity and vitamin D level, a statistically significant association of moderate intensity was identified only in the COVID-19 subgroup (χ = 11. 708, φ = 0. 293, p = 0. 020). In the same subgroup, a significant correlation was found between vitamin D levels and serum potassium values (χ = 10. 527, p = 0. 032). Moreover, in the COVID-19 subgroup, an association between abnormal sodium levels and increased D-dimer levels was found (χ = 7. 074, p = 0. 029). Conclusions: These results underline the importance of monitoring immunologic, vitamin, and electrolyte imbalance in the management of these cases and highlight the need for personalized therapeutic strategies to prevent long-term complications.