Active Surveillance and Polymerase Chain Reaction (PCR) Between Two Passive Surveillance Periods Improve Detection and Characterization of Pleural Empyema: A 20-Year Study in Tijuana, Mexico

Pleural empyema (PE) surveillance was conducted at Tijuana General Hospital in Tijuana, Mexico, across three distinct periods: passive surveillance (2000-2005), active clinical surveillance with the incorporation of polymerase chain reaction (PCR)-based diagnostics (2005-2018), and a subsequent return to passive surveillance (2022-2024). The implementation of active surveillance coupled with molecular diagnostics substantially improved the detection of PE cases and the identification of causative pathogens, while also enabling the evaluation of the impact of pneumococcal conjugate vaccines (PCVs), including the 7-valent vaccine (PCV7; 2005-2012) and the 13-valent vaccine (PCV13; 2012-2018). This integrated approach provided a more accurate characterization of the etiologic spectrum of PE in children and adolescents, improved antimicrobial susceptibility profiling to better inform clinical management, and generated robust evidence supporting the high effectiveness of PCV13. Collectively, these findings highlight the value of sustained active surveillance and molecular diagnostics in strengthening evidence-based decision-making related to vaccine effectiveness, safety, and potential future vaccine implementation within national immunization programs.