Invasive pneumococcal diseases in adults admitted to the Na Bulovce Hospital: Serotype replacement after the implementation of general childhood pneumococcal vaccination.

Objective: The aim of this study was to analyse epidemiological and clinical characteristics of invasive pneumococcal disease (IPD) in adults before and after the introduction of the general childhood conjugate pneumococcal vaccination programme in the Czech Republic.

Material and methods: The retrospective observational sentinel study included adults with IPD admitted to the Na Bulovce Hospital in Prague from 1/2000 through 12/2019. A case of IPD was defined as isolation of Streptococcus pneumoniae from a primarily sterile site.

Results: A total of 304 IPD cases were diagnosed during the study period, with a male to female ratio of 1.49:1 and age median of 58 years (IQR 43-73). The most prevalent clinical forms were bacteraemic pneumonia (185 cases; 60.9%) and purulent meningitis (90; 29.6%). A total of 157/293 patients (53.6%) required intensive care, and the case fatality rate was 25.3% (n = 77). The serotype was determined in 292 (96.0%) isolates, the most prevalent being serotypes 3 (38; 12.5%), 4 (28; 9.2%), 7F (24; 7.9%), 8 (21; 6.9%), and 1 (18; 5.9%). Both clinical and epidemiological characteristics of IPD caused by the most prevalent serotypes differed considerably. Patients diagnosed with serotype 3 were older, more frequently required intensive care, and showed higher mortality. The proportion of IPD caused by non-PCV13 serotypes increased from 28.8% (19/66) in 2000-2005 to 54.8% (40/70) in 2015-2019 (p = 0.001).

Conclusion: The study demonstrated that invasive diseases caused by the most prevalent pneumococcal serotypes differ in their epidemiological and clinical characteristics and case fatality rate. During the study period, there was a significant increase in IPD caused by non-PCV 13 serotypes, limiting the effect of vaccination in adults.