[Immunization for children treated for solid tumors: what are the guidelines?]

Impact of Conventional Chemotherapy on Levels of Antibodies Against Vaccine-Preventable Diseases in Children Treated for Cancer

Intensive chemotherapy in children with malignancies causes partial immune deficiency, including long-term impairment of humoral immunity. We investigated the levels of antibodies against measles, mumps, polio, rubella, diphtheria, tetanus, and Haemophilus type b (Hib) in 139 children at the time of diagnosis of the malignant disease, during chemotherapy, after cessation of intensive treatment, and after re-vaccination. In general, cytostatic therapy resulted in a significant lowering of antibody levels. A decline of antibodies below the protective level as a consequence of cytostatic treatment was observed in 6% of the children for measles and mumps, in 18%, 12%, and 25% for polio types 1, 2, and 3, and in 21% for diphtheria. By contrast, rubella and tetanus antibodies remained within the protective range in all cases of this study. Re-vaccination 3 to 5 months after cessation of chemotherapy produced antibody levels about as high as those measured prior to therapy. Only 6 out of 83 children with previously positive antigen titres did not respond to re-vaccination. Vaccination or re-vaccination failed in 5 of 13 non-responders for more than 1 antigen, indicating a decreased reactability to vaccinations in some patients.

[Yellow fever vaccination in non-immunocompetent patients]

Any person travelling in countries where yellow fever (YF) is endemic and without presenting contra-indication for the vaccination against YF may be vaccinated. This vaccination can very rarely induce a potentially lethal neurotropic or viscerotropic disease. In severely immunodeficient patients, the vaccination is contra-indicated because postvaccinal encephalitis may occur after the vaccination, due to vaccine strain pathogenecity. It is important to evaluate the general health status in elderly individuals before vaccinating because of the increased risk of viscerotropic disease in people of 60 years of age and over. Pregnant women should not be vaccinated, except if departure to an endemic zone is unavoidable. YF vaccinatio is contra-indicated for newborns under six months of age. Solid organ grafts, congenital immunodeficiency, leukemia, lymphoma, cancer, and immunosuppressive treatments are contra-indications for this vaccination. Nevertheless, YF immunization is possible after a bone marrow graft and a two-year period without graft-versus-host disease or immunosuppressive treatment. There is no data to support that immunization of the dono prior to the graft could confer protection against yellow fever to the recipient. Low doses, short courses of corticosteroids either as systemic treatment or intra-articular injections are not contra-indications for YF vaccination. Patients infected with HIV with stable clinical status and T CD4-cel count above 200 cells per millimetre cube may be vaccinated. Thymic diseases, including thymoma and thymectomy, are contra-indications for YF vaccination. Finally, a substantial residual level of antibodies beyond 10 years after the latest vaccination could confer protection, thus avoiding a new vaccination when it is an issue.

Immunizations for children with cancer

Children with malignant diseases are at risk of severe outcomes from vaccine preventable infections. Vaccination of these children presents challenges due to efficacy and safety concerns. There is a paucity of data on several aspects of vaccination in this group of children. Consequently, for the most part, data are extrapolated from healthy populations and combined with experts' opinions. This article reviews the use of vaccines in infants and children with cancer. In this context, an all-encompassing review is not the goal. Key principles are reviewed to provide a framework to guide the use of vaccines in children with malignant diseases.