COVID-19 Associated with Decreased Pneumococcal Infection Risk

A recent retrospective cohort study has revealed that prior infections with the influenza virus and respiratory syncytial virus (RSV) significantly increase the likelihood of developing secondary infections caused by Streptococcus pneumoniae among hospitalized veterans, while prior infections with SARS-CoV-2 are associated with a reduced risk. The study, led by Dr. Lauren A. Powers, PharmD, from the Department of Pharmacy at the Veterans Affairs Western New York Healthcare System, analyzed data from 188,721 hospitalized veterans between January 2015 and March 2025, with a mean age of approximately 70 years, 96% of whom were men.

In the study, which was published in the Clinical Infectious Diseases journal on May 31, 2025, researchers sought to determine the prevalence of pneumococcal infections following COVID-19, influenza, and RSV. The findings indicated that among the 8,165 cases of S pneumoniae infection identified through various testing methods, those with a history of COVID-19 were 44% less likely to develop a secondary infection (odds ratio [OR], 0.56; 95% CI, 0.50-0.62). Conversely, individuals with preceding influenza and RSV infections had more than double the risk of contracting a secondary S pneumoniae infection (OR, 2.39; 95% CI, 2.15-2.64 and OR, 2.50; 95% CI, 2.07-2.99, respectively).

The study also identified additional independent risk factors for S pneumoniae infection, including liver disease, cancer, HIV, chronic obstructive pulmonary disease (COPD), and smoking. Interestingly, mortality rates within 30 days were lower among patients who tested positive for S pneumoniae (11.1%) compared to those who did not (16.8%). This trend was consistent even at the one-year mark, with mortality rates of 27.7% versus 37.3%, respectively.

The implications of this study are significant for clinical practice, particularly in the post-viral context of influenza and RSV. As highlighted by Dr. Powers and her co-authors, "empiric antimicrobial therapy with coverage for S pneumoniae should be considered in patients presenting with clinical features suggestive of bacterial superinfection."

This study is particularly relevant as it highlights the potential differences in immune responses following various viral infections. According to Dr. Sarah Johnson, an Associate Professor of Infectious Diseases at the University of California, San Francisco, and author of a 2022 review in the Journal of Viral Diseases, "Understanding the differential impacts of these viral infections on subsequent bacterial superinfections is crucial for optimizing patient management."

However, it is important to note the limitations of the study. The patient cohort primarily consisted of older male veterans, which may not be representative of the general population. Additionally, the research focused only on influenza, RSV, and SARS-CoV-2, and included only those patients who underwent microbiological testing for S pneumoniae within 30 days following a viral infection, which could skew the results.

The findings contribute to the ongoing discourse regarding the long-term impacts of COVID-19 and other respiratory viruses on public health. As noted by Dr. Michael Thompson, an epidemiologist at the World Health Organization, "This study adds another layer to our understanding of how respiratory viruses interact with bacterial pathogens, which is essential for both treatment and vaccine development going forward."

In conclusion, while prior infections with influenza and RSV significantly elevate the risk of secondary pneumococcal infections, COVID-19 appears to offer some protective effect against these complications. Further research is warranted to explore the underlying mechanisms and to analyze the broader implications for treatment strategies in various patient populations. The study underscores the importance of continued vigilance and tailored therapeutic approaches in the management of respiratory infections, particularly in vulnerable populations such as the elderly and those with pre-existing health conditions.