Background
Containment measures during the COVID-19 pandemic have led to epidemiological changes of respiratory infections. We describe variations over time observed within the multicentric study PNEUMO Europe.

Methods
As part of the ongoing Pneumococcal Pneumonia Epidemiology, Urine Serotyping, and Mental Outcomes (PNEUMO) study, we prospectively enrolled hospitalized adults with CAP from >30 hospitals in Spain, France, Italy, Germany, and the UK. Preliminary data are summarized. Samples for microbiological diagnosis were obtained according to local standard of care. Streptococcus pneumoniae isolates and urine samples were collected for specific serotyping.

Results
From February 2020 to February 2023, 2644 patients were enrolled; 1322 in Spain, 488 in Italy, 436 in France, 307 in the UK and 91 in Germany. The median age was 69 years (IQR 57-79). A presumptive pathogen was detected in 1515 patients (57.2%). The most commonly detected were SARS CoV-2 (25.0%), Streptococcus pneumoniae (14.3%), Influenza (3.5%) and Legionella pneumophila (3.3%). The etiology of CAP varied considerably during the study period. Between August 2020 and July 2021, 46% of CAP hospitalizations were associated with COVID-19 and 8.1% were associated with S. pneumoniae. From August till the end of 2022, COVID-19 hospitalizations decreased to 6.7% and S. pneumoniae hospitalizations increased to 19%.

Conclusion
The proportion of CAP hospitalizations associated with S. pneumoniae decreased during the COVID-19 pandemic, but rapidly increased again after COVID-19 hospitalizations decreased. By the end of 2022, S. pneumoniae was the most commonly detected organism in CAP.