Streptococcus pneumoniae bacteremia: comparison of incidence, epidemiology, and clinical outcome in a pre- and post-COVID-19 period

Objectives: Streptococcus pneumoniae is a leading cause of severe bacterial infections, including pneumonia, meningitis, and bacteremia. We aimed to evaluate the differences in clinical, epidemiological and outcome manifestations of patients admitted with S. pneumoniae bacteremia (SPB) in the pre- and post-COVID-19 period. Methods: The study analyzed all patients admitted in Province of Modena, Italy, during two time-periods: pre-COVID-19 (Jan 2018- Feb 2020) and post-COVID-19 (Mar 2020- Jun 2022) period. The data were compared using univariate and multivariate analysis. Results: A total of 150 patients with SPB were included, 109 and 41 patients in the pre- and post-COVID-19, respectively. We observed a decrease in SPB incidence from March 2020, after the implementation of the restrictive measures for the COVID-19 pandemic, and a new increase since Jun 2021, when lockdown measures were fully lifted. SPB was associated with pneumonia in 128 patients (85.3%), meningitis in 25 (16.7%) and otitis-mastoiditis in 14 (9.3%). The proportion of patients presenting with multi-lobar pneumonia significantly increased during the post-COVID-19 period (39.0% vs. 16.5%, p = 0.008). Thirty-day mortality rate resulted higher in the post-COVID-19 period (24.4% vs. 11.9%, p = 0.075), and multivariate analysis identified an age ≥ 80 years (OR 4.45, 95% CI 1.12–17.61, p = 0.033), multi-lobar pneumonia (OR 4.34, 95% CI 1.56–12.07, p = 0.005), and central nervous system disease (OR 3.63, 95% CI 1.08–12.20, p = 0.036) as independent risk factors for 30-day mortality. The rate of pneumococcal vaccination in the at-risk population was low (9.3%), but in the pandemic period the rate increased by 26.7%, driven by the anti-SARS-CoV-2 vaccination campaign. Conclusions: The COVID-19 pandemic has impacted the epidemiology and clinical severity of SPB. In our study, less than 10% of the high-risk population was vaccinated, while the older population (age ≥ 80 years) had a significantly higher 30-day mortality risk. It would be necessary for Institutions to increase awareness campaigns for pneumococcal vaccination.