LAUSR

Background: In 2006 a 7-valent pneumococcal conjugate vaccine (PCV7) was introduced in the immunization schedule in The Netherlands for infants and replaced by PCV10 in 2011. Aims and objectives: To describe the overall changes in microbial etiology, pneumococcal burden (including non-bacteremic pneumococcal pneumonia) and its serotypes in adult community-acquired pneumonia (CAP) after the introduction of these PCVs. Methods: Hospitalized adult CAP patients who participated in three consecutive trials were studied (2004-2006 (n=201), 2007-2009 (n=304) and 2012-2016 (n=300); considered as pre-PCV7, PCV7 and PCV10 period). Extensive microbiological work-up was applied for all patients. Changes in proportions of causative pathogens and distributions of pneumococcal serotypes were calculated. Results: The proportion of pneumococcal CAP decreased from 37 to 26% comparing the pre-PCV7 period with the PCV10 period (p=0.01). For other pathogens, including Legionella spp., Mycoplasma pneumoniae, S.aureus, H.influenzae, and respiratory viruses, no sustained shifts were observed in their relative contribution to the etiology of CAP. Within the pneumococcal CAP patients, we observed a decrease in PCV7 and an increase in non-PCV10 serotype disease. Importantly, PCV7 type disease decreased both in bacteremic and non-bacteremic patients. Conclusions: PCV introduction in infants impacts the microbial etiology of adult CAP.