Trends of invasive pneumococcal disease and its serotypes in the Autonomous Community of Madrid

Abstract

IntroductionStreptococcus pneumoniae is an important cause of morbidity. Vaccination is the most effective measure to prevent it. The aim of this study is to analyse the evolution of invasive pneumococcal disease (IPD). Material and methodsObservational study of IPD cases notified to the Epidemiological Surveillance Network of the Autonomous Community of Madrid between 2008 and 2015. The IPD case was defined as the disease caused by S. pneumoniae, with isolation and DNA or antigen detection, in samples from normally sterile sites. The isolated strains were sent to the Regional Public Health Laboratory for identification of the serotype. Serotypes were classified according to their inclusion in the 7-valent conjugate vaccine (PCV7), in the 13-valent vaccine, but not in the 7-valent vaccine (PCV13-additional) and not included in the 13-valent vaccine (non-PCV). The incidence rate ratios (IRRs) were calculated comparing the 2011–2012 and 2013–2015 periods with the 2008–2010 period. Results4,307 cases were reported. 86.6% were serotyped. The IRR of IPD was 0.67 and 0.67 for all serotypes; 0.43 and 0.45 for PCV7 serotypes; 0.46 and 0.25 for PCV13-additional serotypes, and 1.01 and 1.32 for non-PCV13 serotypes in the 2011–2012 and 2013–2015 periods. The incidence of serotypes 8, 9N, 10A, 23B, 24F and serogroup 33 increased significantly in the 2013–2015 period. Serotypes 15B and 24F accounted for 24% of non-PCV13 cases in children under 5 years, serotypes 8 and 9N for 51% in the population aged 5–59 years and serotypes 8 and 22F for 25% in the population aged over 59 years. ConclusionsThe incidence of serotypes not included in conjugate vaccines has increased, especially in children under 5 years, but the total incidence of IPD has decreased. It is important to continue with the epidemiological and microbiological surveillance programmes to assess the effect of vaccination on the incidence of IPD.