[Cytogenetic study of blood lymphocytes in children revaccinated against smallpox]

As the result of primary re-immunization with small-pox vaccine of eight years' old children chromosome aberrations were observed in their peripheral blood lymphocytes, the frequencies being 5.3% and 7.9% on the seventh day and in a month after the reimmunization respectively. Chromosome aberrations were significantly more rare in children with a high level of immunity retained after the preceding immunization as compared to those whose immunity was weakened with time. After the elapse of 6 months following the re-immunization the frequency of chromosome aberrationd did not exceed the initial level. The changes observed in the chromosome apparatus of lymphocytes are not specific for the small-pox vaccine alone, but are the evidence of the disturbance of homeostasis of the microorganism as the result of the effect of an alien antigen.