BACKGROUND: Treatment for pediatric malignancies has distinct effects on the immune system. AIMS: Our aim was to measure humoral immunity to measles, mumps and rubella (MMR), and diphtheria, tetanus and acellular pertussis (DTaP) vaccines after pediatric cancer treatment. METHOD: We assessed IgG titers of 52 children against the vaccine antigens post-treatment. RESULTS: After completed primary vaccination series for MMR and DTaP before treatment, post-treatment there was a considerable proportion of patients with below-reference titers against pertussis, diphtheria and tetanus, but only few subjects showed below-reference titers against measles, mumps and rubella. Our findings may have implications when considering re-vaccination policies.