A multicenter study on the epidemiology of complicated parapneumonic effusion in the era of currently available pneumococcal conjugate vaccines

Background: Parapneumonic effusion (PPE) is a common complication of pneumonia. Streptococcus pneumoniae is the most common cause of bacterial pneumonia. A reduction in pneumonia hospitalizations has been observed since the introduction of the 7-valent pneumococcal conjugate vaccine (PCV7). Despite this apparent benefit, an increase in the incidence of PPE was recorded in some countries following PCV7 implementation. As the 13-val-ent pneumococcal conjugate vaccine (PCV13) was expected to provide a wider protection against PPE, the aim of the present study was to evaluate the impact of PCV13 introduction on the epidemiology of complicated para-pneumonic effusion (c-PPE) among children in the Athens greater area. Methods: All cases of community-acquired pneumonia (CAP) with PPE requiring chest tube insertion (compli-cated PPE, c-PPE) hospitalized in the 3 public Children's hospitals in Athens between 01/01/2004 and 31/12/ 2019 were included in the study. Results: A total of 426 cases of c-PPE associated with pneumonia were recorded of which 198 were admitted during 2004-2010 (period A, prePCV13/PCV-7 introduction period) and 228 during 2011-2018 (period B, post -PCV13 period). A definite bacterial etiology was established in 44.4 % of all cases and of those 25.4 % were caused by S. pneumoniae. An increasing trend in c-PPE incidence was observed during period A; although, a significant decrease on c-PPE annual rates was observed during the period B (p = 0.011), a remarkable increase in serotype 3 cases was recorded. Conclusion: A decreasing time trend in c-PPE cases among children was shown after the introduction of PCV13 in our area. However, serotype 3 is nowadays a common cause of PPE. Hence, continuous surveillance is imperative in order to follow c-PPE epidemiology over time.