The drop in reported invasive pneumococcal disease among adults during the first COVID-19 wave in the Netherlands explained.

Objectives: Streptococcus pneumoniae is the leading bacterial pathogen causing respiratory infections. Since the COVID-19 pandemic emerged, less invasive pneumococcal disease (IPD) was identified by surveillance systems worldwide. Measures to prevent transmission of SARS-CoV-2 also reduce transmission of pneumococci, but this would gradually lead to lower disease rates. Design: Here, we explore additional factors contributing to the instant drop in pneumococcal disease cases captured in surveillance. Results: Our observations on referral practices and other impediments to diagnostic testing indicate that residual IPD has likely occurred but remained undetected by conventional hospital-based surveillance. Conclusions: Depending on the setting, we discuss alternative monitoring strategies that could improve understanding of pneumococcal disease dynamics.