Objective: Cancer treatment in children leads to failure to complete the childhood vaccination program and weakening or loss of vaccine-acquired immunity. Post-treatment vaccine responses of children receiving cancer treatment vary. In this study, we aimed to investigate serum antibody status, and vaccine responses in children after cancer treatment. Methods: Pediatric patients who were admitted to Hacettepe University Hospitals between January 1, 2015, and December 31, 2020, who received chemotherapy for lymphoma and solid organ tumors, and whose diseases were in remission were included in the study. Vaccines administered after cancer treatment, hepatitis A (HAV), hepatitis B (HBV), varicella zoster (VZV), measles-mumps-rubella (MMR) serum antibody levels, and changes in vaccine responses after treatment were retrospectively investigated. Results: The study included 533 patients. After treatment, measles, HAV, rubella, HBV, VZV, and mumps, seronegativity were found in 83.5%, 64%, 60.1%48,5%, 43.3%, and 28%of the patients, respectively. Post-treatment rates of antibody loss in descending order were measles (47.1%), HAV (31.9%), HBV (31.4%), mumps (28.6%), VZV (21.7%), and rubella (11.4%). Seroconversion rates to one dose of vaccines in descending order, were (83.6%), rubella (82.9%), HBV (81.4%), VZV (63.5%), mumps (45.4%), and measles (33.3%). Seroconversion rates to two doses of the same vaccines, in descending order, were: HAV (98.8%), VZV (84.6%), rubella (80%), HBV (80%), measles (32.2%), and mumps (36.2%) Conclusion: Serologic vaccine responses of patients after treatment were lower than expected even with repeated doses. As these patients may require intermittent serologic evaluations and repeated vaccinations according to their risk status, we have planned longer-term follow-ups of them.

Castleman disease is a rare, heterogeneous disorder that driven by proinflammatory responses. Human herpes virus-8 has a major role in pathogenesis of multicentric Castleman disease. There is also a subgroup of cases, human herpes virus-8 negative, idiopathic multicentric Castleman disease. The role of primary immunodeficiencies in idiopathic Castleman disease are poorly described. DOCK8 deficiency is a combined primary immunodeficiency. It has a broad clinic spectrum including atopy, autoimmunity and cancer. We present a 10-year-old, DOCK8 deficient patient. He had giant lobular capillary hemangiomas on his neck, iliac and gluteal regions and multiple lymphadenopathies. Abdominal lymph node pathology revealed hyaline vascular type Castleman disease and human herpes virus-8 staining was negative. His lesions were shown to be infected with orf virus. Our case is the first case to relate idiopathic multicentric Castleman disease and DOCK8 deficiency; also, very unusual presentation of orf virus infection in humans.