Abstract. One hundred and seven children (45 girls and 62 boys) in the age of 20 months — 14 years old (mean 9,62±0,37) suffered from acute lymphoblast leukosis and solid tumors in history have been examined in the clinic of Research Institute of children infections of FMBA. The vaccination history was studied in all children and the titers of specific antibodies to measles and mumps viruses as well as immune status were determined. 83,8% and 85,4% of studied children had no protection against measles and mumps respectively or had low titers of antibodies. Immunological examination of these children conducted within 4 months after finishing of therapy revealed absence of immunodeficiency. It gave opportunities to vaccinate or revaccinate these children against mentioned infections. Fifty three children were immunized against measles and 47 — against mumps. Application of live vaccines was safe because majority of vaccinated against measles (81,1%) and mumps (82,9%) children had mild vaccination process. It was established that to increase immunological efficacy of vaccination using of polyoxidony during 5 days before vaccination and 5 days after vaccination is reasonable.