A Personalised Vaccination Program Based on Immune Reconstitution in Paediatric Cancer Survivors

Aims: Paediatric cancer survivors often experience treatment-induced immunosuppression, requiring post-treatment revaccination. However, immune recovery timelines vary, and current revaccination guidelines, largely based on data of varied quality derived from studies on acute-lymphoblastic-leukaemia (ALL), may not be applicable across all paediatric malignancies. This study evaluated a personalised revaccination approach based on immune recovery. Methods: Immune recovery was evaluated using antibody titers to common childhood vaccines, immunoglobulin levels, B- and T-cell subpopulations, and T-cell receptor excision circles (TREC) and kappa-deleting recombination excision circles (KREC) markers. The recommended revaccination window was defined as 3–6 months post-treatment. Patients completing immune and serology testing within this window were categorised as the per-protocol-group (PPG), while others were categorised as the protocol-deviated-group (PDG). Results: Among 19 PPG patients, 57.9% required major and 36.8% minor modifications to recommended revaccination guidelines, with major modifications more common among hematologic malignancies than solid tumours (83.3% vs. 46.2%, p < 0.0001). In the intention-to-treat (ITT) cohort (n = 52), 40.4% required major and 57.7% minor modifications; hematologic survivors again had higher rates of major modifications (52.9% vs. 34.3%, p = 0.008). Conclusions: Immune recovery following paediatric cancer therapy is highly variable, particularly among hematologic malignancies. Personalised revaccination strategies incorporating comprehensive immunological workups may optimise protection against vaccine-preventable diseases.