Improving patient outcomes in community-acquired pneumonia

The epidemiology of community-acquired pneumonia (CAP) and the spread of pneumococcal serotypes keeps evolving. Therefore, continued work is necessary on improving diagnostic tools, improving serotype surveillance in CAP, and optimizing ways to use biomarkers in clinical care to improve outcomes for patients with CAP. These were the conclusions by Lisa Hessels (UMC Utrecht and Noordwest Ziekenhuisgroep) in her PhD thesis that she defended on January 13, 2026.

Community-acquired pneumonia (CAP) remains a major cause of illness and death worldwide, particularly among the elderly and individuals with underlying conditions. Streptococcus pneumoniae is the most common bacterial cause of CAP, but viruses such as influenza, respiratory syncytial virus (RSV), and COVID-19 also play a significant role. While pneumococcal vaccines reduce the impact of pneumococcal disease, the burden remains high, in both invasive and non-invasive disease, partly due to infection with pneumococcal serotypes not included in currently available vaccines. CAP also leads to significant healthcare costs, a burden likely to grow with ageing populations. Lisa Hessels, MD (Research Program Epidemiology of Infectious Diseases and Department of Pulmonary Medicine, Noordwest Ziekenhuisgroep, Alkmaar) investigated in her PhD project – using data from the ongoing Pneumococcal Pneumonia Epidemiology, Urine Serotyping and Mental Outcomes (PNEUMO) study – how frequently pneumococcal pneumonia occurs, which S. pneumoniae serotypes are circulating, and what their disease burden is.

Changing incidence during the pandemic

During the COVID-19 pandemic, the number of pneumonia cases due to S. pneumoniae initially dropped sharply but increased again after the first year of the pandemic when SARS-CoV-2 cases started to decline. Pneumococcal serotypes 3, 11A, and 8 were found most frequently, some of which are not yet included in current vaccines. Thus, the inclusion of additional serotypes in future pneumococcal vaccines could potentially contribute to improved disease prevention and reduced healthcare burden, and warrants further investigation.

Value of biomarkers

A second theme of Lisa’s thesis focused on the use of biomarkers to improve pneumonia treatment. The biomarker procalcitonin (PCT) proved valuable in reducing unnecessary antibiotic use among COVID-19 patients without negatively affecting outcomes. However, in patients with influenza or RSV infection, the added value of PCT was less pronounced, limiting its utility for optimizing antibiotic use in such viral infections. Other biomarkers, such as soluble urokinase plasminogen activator receptor (suPAR) – a marker of immune activation – demonstrated only limited usefulness in predicting disease prognosis.

Diagnostic decision rules

Finally, Lisa Hessels evaluated the applicability of diagnostic decision rules (YEARS algorithm and Wells’ criteria) for excluding pulmonary embolism (PE) in COVID-19 patients. The efficiency of the prediction rules was comparable to previous studies in non-COVID-19 patients. However, the failure rates suggest that, irrespective of the method used to exclude PE, a reassessment of the clinical probability of PE is needed in COVID-19 patients with clinical deterioration after recent PE exclusion.

Improving patient outcomes

In her conclusion Lisa Hessels said: “The epidemiology of CAP and the spread of pneumococcal serotypes keeps evolving. While vaccines have been highly effective in reducing the burden of certain serotypes, new serotypes not covered by the vaccines are becoming more common. This means that ongoing monitoring and updates to vaccine strategies are necessary. Additionally, biomarkers like PCT and suPAR may help diagnose and treat CAP more effectively, although using them in everyday clinical practice still presents some challenges. The goal remains to reduce antibiotic therapy in viral respiratory infections. We should therefore continue to work on improving diagnostic tools, improving serotype surveillance in CAP, and optimizing ways to use biomarkers in clinical care to improve outcomes for patients with CAP.”