Loss of measles, mumps, and rubella immunity in pediatric cancer survivors following chemotherapy

Fifty-four pediatric cancer survivors (mean age 12.5 years) were evaluated at a median of 2.5 years (IQR 1.2, 5.4) after completing chemotherapy. All participants had received at least one MMR dose before their cancer diagnosis and had completed treatment at least six months prior. 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 observed for mumps or rubella seronegativity. These findings indicate a substantial decline in MMR immunity after chemotherapy and support the incorporation of routine post-chemotherapy revaccination into survivorship care, especially in settings where serologic testing is not readily available.