Aim: The second dose of measles vaccination has been performed since 1998 in Turkey. As a result of measles vaccination campaign in schools (MVCS) between September to October 2003, the children vaccinated once or twice before campaign would be vaccinated once more. We planned to investigate the immunity provided by campaign and the influence of vaccination on the hematological parameters. Materials and Method: Blood samples were taken one month before and after MVCS. Measles antibody titres and whole blood counts (leukocyte counts, hemoglobin level, hematocrit, thrombocyte counts, mean corpuscular volume and red cell distribution width) were evaluated. The individuals were classified according to previous vaccination number and to socioeconomic status such as low or high. A total of 164 cases were enrolled in the study and hematological parameters were evaluated in 119 children. Results: The mean age of 164 cases (79 males, 85 females) was 11.3±1.8 years. The measles seropositivity increased from 95.04% to 99.38% after MVCS (p=0.039). Leukocyte counts reduced from 8.04±1.95×109/L to 7.07±2.04x109/L (p<0.001), and hemoglobin increased from 12.98±0.90 g/ dL to 13.73±0.94 g/dL (p<0.001) after MVCS. It has been shown that red blood cells and platelet counts were decreased (p<0.001 and p<0.001, respectively), and mean corpuscular volume and red cell distribution width were increased (p<0.001 and p<0.001, respectively) after MVCS. Conclusion: The 95% vaccination ratio recommended by WHO was attained after MVCS in our study population. It must be kept in mind that measles vaccination can decrease leukocytes and platelets after MVCS. © The Journal of Current Pediatrics, published by Galenos Publishing. All rights reserved.