Evolution of pneumococcal infections in adult patients during a four-year period after vaccination of a pediatric population with 13-valent pneumococcal conjugate vaccine

Abstract

Objectives: To describe the distribution of vaccine and non-vaccine pneumococcal serotypes from adult patients for different clinical scenarios, after the introduction of the 13-valent pneumococcal conjugate vaccine (PCV-13) for children. Methods: This was a prospective study of pneumococcal infections in adult patients (January 2010 to April 2014) in Hospital Son Llatzer, Mallorca (Spain). Two different periods of time were compared, the first before (first period) and the second after (second period) the introduction of PCV-13. Information related to clinical characteristics, outcomes of infection, pneumococcal serotypes, and antibiotic susceptibility was collected. Results: We studied 407 episodes (371 patients), 201 in the first period and 206 in the second period. The majority of patients were male; the median patient age was 68 (range 15-99) years. Infections due to PCV-13 serotypes decreased from 59.7% to 47.6% (p = 0.014), mainly serotypes 3, 7, 18C, 19F, and 23F. In the second period, PCV-13 serotypes were the cause of pneumonia in 58.2% of cases and in 40.8% of invasive infections, but these serotypes were not related with any outcome variable. No differences in hospital or intensive care unit admission, severity, or mortality were observed between the two periods. Susceptibility to penicillin (98.2% vs. 95.1%, p = 0.03) and amoxicillin (96.5% vs. 91%, p = 0.007) was slightly higher in the first period. Conclusions: Although a reduction in infections due to vaccine serotypes was observed, close to half of infections in adult patients were caused by PCV-13 serotypes. Even after pediatric vaccination with PCV-13, vaccine serotypes were still responsible for most pneumonia and invasive disease, underscoring the importance of implementing current guidelines and extending vaccination to other risk groups.