Infections caused by antibiotic-resistant strains of Streptococcus pneumoniae are less treatable, which can lead to adverse clinical outcomes and increase the economic cost of conducting treatment. Worldwide, the development of most infections caused by penicillin-resistant strains of S. pneumoniae is responsible for five of the seven serotypes included in the pneumococcal conjugate vaccine (6B, 9V, 14, 19F and 23F) introduced into clinical practice in 2000. The relationship between the serotype and the level of resistance of pneumococci suggests that the use of a vaccine, as well as the development of immunity against these microorganisms, will help to reduce the incidence of infections caused by resistant strains of pneumococci.

The aim of the study by M.H. Kyaw et al. (USA), was to study the effect of vaccination on the incidence of invasive infections caused by resistant strains of S. pneumoniae. The researchers used the data obtained during the observational study "Active Bacterial Core Surveillance" for the period from 1996 to 2004. The isolated pneumococcal strains were serotyped and tested for sensitivity.

The study found that the frequency of detection of invasive infections caused by penicillin-insensitive strains and polyresistant strains of S. pneumoniae was highest in 1999, from 6.3 to 2.7 cases in 2004 per 100,000 (57% decrease; 95% confidence interval 55-58%) and 4.1 to 1.7 cases per 100,000 (59% decrease; CI at 95% 58-60%), respectively. There was also a decrease in the incidence of infections caused by penicillin-insensitive strains in children under 2 years of age from 70.3 to 13.1 cases per 100,000 (81% decrease; 95% CI % 80-82%) and people aged 65 years. years and over from 16.4 to 8.4 cases per 100,000 (a decrease of 49%). The incidence of infections caused by resistant serotypes included in the vaccine increased from 5.0 to 0.7 per 100,000 (87% decrease; 95% CI 86-88%). At the same time, the incidence of infections caused by serotype 19A, which is not included in the vaccine, increased from 2.0 to 8.3 cases per 100,000 children under 2 years of age.

The data obtained during the study indicate that the introduction of a pneumococcal conjugate vaccine in clinical practice has led to a decrease in the incidence of invasive pneumococcal infections resistant to antibiotics in general, but to an increase in the incidence of infections caused by resistant strains not included in the vaccine.