Healthcare-associated infections in U.S. hospitals declined by 27% between 2015 and 2023, according to a study conducted by researchers at the Centers for Disease Control and Prevention (CDC) and published in the New England Journal of Medicine. The reduction represents a public health achievement, with an estimated 471,555 hospital patients affected by at least one healthcare-associated infection in 2023, down from higher levels eight years earlier.

The study analyzed data from national surveys conducted in 2015 and 2023, finding that the proportion of patients with at least one healthcare-associated infection on any given day dropped from 3.2% in 2015 to 2.6% in 2023. In a subset of 151 hospitals that participated in both surveys, adjusted analyses showed patients were 27% less likely to have a healthcare-associated infection in 2023 compared to 2015, corresponding to a risk ratio of 0.73 with a 95% confidence interval of 0.63 to 0.85.

Specific types of infections showed marked declines over the period. The prevalence of Clostridioides difficile infections fell from 0.54% in 2015 to 0.22% in 2023. Central catheter-associated bloodstream infections decreased from 0.30% to 0.16%, and catheter-associated urinary tract infections dropped from 0.20% to 0.09%. Researchers attributed the decline in Clostridioides difficile infections likely to hospitals adopting more two-step testing methods, which offer higher specificity than older one-step tests.

Despite overall progress, not all infection categories improved. The percentage of patients with surgical-site healthcare-associated infections rose slightly from 0.56% in 2015 to 0.59% in 2023. This exception underscores a key focus area for future prevention efforts. In 2023, there were an estimated 518,000 healthcare-associated infections overall in U.S. hospitals, with pneumonia remaining the most common type in both survey years.

Device-related infections saw substantial reductions as a share of total healthcare-associated infections. The percentage of device-related bloodstream infections dropped from 73% in 2015 to 47% in 2023, while device-related urinary tract infections fell from 62% to 34%. Meanwhile, the share of infections not linked to a specific procedure or device increased slightly, from 60.2% in 2015 to 61.3% in 2023. Among pneumonia cases, non-ventilator-associated infections constituted 64.5% in 2015 and 65.7% in 2023, though the overall percentage of patients with non-ventilator-associated pneumonia decreased from 0.58% to 0.49%.

Pathogen data from the 2023 survey showed that 51% of identified healthcare-associated infection pathogens were Staphylococcus aureus, Escherichia coli, or Clostridioides difficile. Staphylococcus aureus was the most common single pathogen, accounting for 13.8% of infections. Clostridioides difficile’s share of total infections also declined sharply, from 15.5% in 2015 to 7.7% in 2023.

The surveys underpinning the study were conducted through the CDC’s Emerging Infections Program, drawing data from hospitals in 10 states. The 2015 survey included 12,299 patients across 199 hospitals, while the 2023 survey covered 13,653 patients in 218 hospitals. Hospitals selected a single survey day between May 1 and September 30, 2023, and randomly chose patients from the morning census for inclusion. Researchers used definitions from the CDC’s National Healthcare Safety Network to identify infections.

Demographic and clinical characteristics of surveyed patients also shifted slightly. In 2015, 65.2% of patients were age 45 or older, a figure that rose to 71.6% in 2023. The mean hospital stay increased from 5 days in 2015 to 6 days in 2023. In the 2023 survey, 62.8% of patients were white, 73.5% were in a ward, and 68.4% were treated in medium or large hospitals.

Nora Chea, MD, of the CDC Division of Healthcare Quality Promotion, noted the broader implications of the findings. “The reduction in prevalence provides evidence of continued success of prevention strategies,” she said. She added that “additional interventions focusing on prevention of surgical-site infections and health care-associated infections that are not associated with devices or procedures are recommended to further reduce the risk of healthcare-associated infections in hospitals.”

The study authors also ongoing challenges in surveillance. “A major challenge to evaluating prevention measures and tracking progress in reducing non-ventilator-associated pneumonia is the lack of a surveillance definition based on data elements that are readily retrievable from electronic health records,” they wrote. However, they pointed to promising developments: “Recent work to develop such a definition provides a foundation for a potential national digital quality measure in the future.”

The decline in healthcare-associated infections reflects years of coordinated prevention efforts across U.S. hospitals, including improved hand hygiene, catheter care protocols, and antimicrobial stewardship. These infections not only endanger patient safety but also increase hospital stays, healthcare costs, and mortality. The study’s findings validate the effectiveness of existing strategies while identifying surgical-site and non-device-related infections as priority areas for further intervention.

However, the authors acknowledged limitations: changes over time in National Healthcare Safety Network definitions may affect trend interpretation, and the results may not be generalizable to all U.S. hospitals since data came from a subset participating in the Emerging Infections Program. Nonetheless, the consistent methodology across the two surveys strengthens confidence in the reported 27% decline.