Abstract Nucleic acid amplification tests (NAATs) greatly enhance the capacity to identify the etiology of pediatric complicated pneumonia. However, the use of pneumococcal conjugate vaccines could reduce the importance of Streptococcus pneumoniae in pediatric complicated pneumonia with the potential emergence of other bacterial agents. Using an expanded NAAT in culture negative pleural fluid or empyema samples collected in 2010–2024 (n = 554) in Portugal, we show that S. pneumoniae remains the most frequent agent despite decades of pneumococcal conjugate vaccine use and the COVID-19 pandemic. A rebound in pediatric complicated pneumonia occurred post-pandemic, including a rise in cases by Streptococcus pyogenes and Haemophilus influenzae. Empiric therapy of pediatric complicated pneumonia should still consider S. pneumoniae as the most likely cause, even in countries where the pneumococcal conjugate vaccine is in the national immunization program with a high uptake.
