Loss of Measles, Mumps, and Rubella Immunity in Pediatric Cancer Survivors Following Chemotherapy

Objectives Pediatric cancer survivors are at increased risk for vaccine-preventable diseases due to treatment-related immunosuppression. This study aimed to assess serological status for measles, mumps, and rubella (MMR) following chemotherapy and identify factors associated with antibody loss. Results A total of 54 pediatric cancer survivors (mean age 12.5 years) were evaluated for humoral immunity at a median of 2.5 years (IQR 1.2–5.4) after completing chemotherapy. All participants had completed treatment at least six months prior and had received at least one dose of the MMR vaccine before their cancer diagnosis. Overall, 43 patients (79.6%) were seronegative for at least one MMR component. Seronegativity was highest for measles (64.8%), followed by mumps (55.6%) and rubella (35.2%). Measles seronegativity was significantly associated with a longer interval since chemotherapy (> 5 years; p = 0.04) and older age at receipt of the second MMR dose (mean 86.4 vs. 44.9 months; p = 0.002). No significant associations were identified for mumps or rubella seronegativity. Conclusions A substantial proportion of pediatric cancer survivors lacked protective MMR immunity, particularly against measles. These findings support the implementation of routine revaccination strategies in survivorship care without the need for prior serologic testing.