Dynamics of Streptococcus pneumoniae serotype structure in children for the period 2016-2022

Abstract

Background. The need for microbiological monitoring of the distribution of pneumococcal serotypes is associated with changes that occur during routine immunization of children with pneumococcal vaccines. Aim. To characterize the changes in the serotype structure of S. pneumoniae obtained from healthy preschool children from 2016 to 2022. Materials and methods. Nasopharyngeal isolates of pneumococcus (n=265) were obtained from 1250 healthy children under 6 years of age attending kindergartens. Serotype structure of S. pneumoniae was performed using PCR. Results. During 2016-2018, the prevalence of pneumococcal carriage was decreased from 27.3% to 17.3%, and by 2022 it was increased again to 25.6%. At the same time, the correspondence of S. pneumoniae serotypes to the antigenic composition of the 13-valent pneumococcal vaccine was decreased from 48.8% to 9.4%, and to the composition of the 20-valent vaccine – from 75.6% to 39.1%. The proportion of “non-vaccine” types of pneumococcus, accordingly, increased from 22% in 2016 to 61% in 2022. Among the “non-vaccine” serotypes/groups, 15AF, 6CD, 23A and 35F/47F were predominated, and new variants were also discovered: 23B and 35B. The serotypes included in the 13-valent conjugate vaccine were detected, as a rule, among unvaccinated children and were represented by variants 19F, 6A and 6B, 23F. Throughout the observation period, pneumococci of serotypes/groups 15BC, 11AD and 10A were detected with high frequency. Conclusions. During 2016-2022, due to the elimination of a significant part of the “vaccine” S. pneumoniae serotypes, there was a significant decrease in the compliance of circulating pathogen variants with the antigenic composition of the used conjugate vaccines. At the same time, new types that are detected with high frequency are not included in existing pneumococcal vaccines which necessitates the creation of new immunobiological drugs.