Objective. The study objective is to establish the epidemiological features of Streptococcus pneumoniae carrier of different serotypes in organized children groups during vaccinal prevention. Methods. 1574 children were examined on the nasal S. pneumoniae carriage aged 2-7 y.o., having gone to preschool institutions of St. Petersburg. Results. The percentage of S. Pneumoniae serotype strains covered by the action of 13-valent vaccine, was 36.03 %, that is lower than corresponding value (65.4 %), determined in a similar design study in St. Petersburg in 2010-2013. At the same time, it remained unclear whether this reduction could be considered the result of vaccine prevention, since the level of coverage with preventive vaccinations in the studied population was then quite low. Conclusions. The wide spread of pneumococcal serotypes, unreached by the action of the 13-valent pneumococcal vaccine, on the one hand, indicates the need for constant monitoring of the pathogen population during mass immunization programs, and on the other hand, it makes it possible to raise the question of the need to expand the antigenic repertoire of the vaccines used.