[Long-term observations of dynamics of collective immunity to poliomyelitis in vaccinated children].

Examinations of children in the Moscow region in 1972 revealed low values of the herd immunity to poliomyolitis. This was suggested to be due to improper organization of vaccination of children. The regional health authorities took special measures for better organization of vaccination. The examinations two years later, in 1974, showed nearly 90% of children between the ages of 1 and 6 years to have antibody to all three types of poliomyelitis virus. The geometric mean antibody titre increased. In children of 10--14 years the heard immunity values did not differ significantly from those found in 1972. It is concluded that proper vaccination gives sufficiently intensive immunity nearly in 90% of children. It was found that in children vaccinated 10--12 times the herd immunity persists without significant changes for 3 years after the last vaccine feeding; at 4 years, however, some values of the herd immunity, particularly to poliomyelitis virus type III, were significantly lower than the original values. It is suggested that it is likely to be expedient to revaccinate 4-grade schoolchildren and to reduce the total number of vaccine feedings during the first 4 years of life.