The coronavirus disease 2019 (COVID-19) pandemic has led to major disruptions in healthcare. It brought large waves of critically ill patients, cared for in an already stressed healthcare environment. Addressing the high transmission risk of the disease, its severity, and its complex management, clinically and operationally, had a substantial impact on the healthcare workforce and their function. Many experienced personnel exited the workforce, often replaced by new potentially less skilled members. In addition, alterations in processes, supply chain shortages, and measures to mitigate transmission risk or build capacity disrupted established systems for patient care delivery resulting in diminished interactions between healthcare workers and patients. ^{Reference Dang, Thakker, Li, Hommel, Mehta and Goodwin1,Reference Iness, Abaricia and Sawadogo2} Since the early pandemic period, healthcare resilience, defined as the ability to adjust and sustain operations under expected and unexpected conditions, ^{Reference Tan, Prager, McClelland and Dark3} has been an important element to assess readiness and response to major challenges to healthcare systems. Resilience can be considered at three levels, the individual, the hospital or organizational, and state or national levels. Sapiano et al. ^{Reference Sapiano, Dudeck and Patel4} addressed US hospitals resilience using central line associated bloodstream infections (CLABSI) as a surrogate. They evaluated the impact of four stressors, critical staff shortages, hospital inpatient COVID-19 occupancy rate, its sustained high inpatient occupancy rate, and its community burden in the early pandemic on CLABSI outcomes, a surrogate for patient safety. The authors found a higher CLABSI rate for larger hospitals, a disproportionately higher rate for patients cared for in critical care units, and lower rates for patients in surgical hospitals. Both critical staff shortages for >10% of hospital days per month and COVID-19 inpatient occupancy ≥20% were associated with higher CLABSI rates. They also found that high COVID-19 community rates and sustained high inpatient occupancy rates were associated with worse CLABSI outcomes. One of the limitations of the study is the inability to address the difference in outcomes for patients with COVID-19 infections and those not documented to be infected. ^{Reference Sands, Blanchard, Fraker, Korwek and Cuffe5,Reference Sturm, Saake, Roberts, Masoudi and Fakih6} Still, the authors highlight the cardinal value of addressing hospital characteristics and preparedness in facing pandemics or other disasters. They advocate for the importance of national reporting of COVID-19 and other stressors that may affect hospital resilience. The study provides first good steps to better understand factors that impact the readiness of hospitals to cope with stressors such as pandemics.

The study indirectly addresses resilience of US hospitals, using one healthcare-associated infection- CLABSI, and brings an element that we have hardly seen prior to the pandemic, the instability of workforce and consequently more risk for safety events, particularly infectious complications. More studies are needed to evaluate the measures that may correlate with safety outcomes in hospital settings. The increase in CLABSI events may be predominantly attributable to the COVID-19-infected patients admitted to the hospital, with a sizable proportion of them requiring intensive care and support, and prolonged length of stay. In one study of a large system, hospital-onset bloodstream infections were more than three times higher for COVID-19-infected compared to non-infected patients. ^{Reference Sturm, Saake, Roberts, Masoudi and Fakih6} The CLABSI risk may be increased based on the characteristics of COVID-19-infected patients, with their higher acuity requiring complex care (eg the frequency of central line access and manipulation, and the use of immunosuppressive agents). Potential additional outcomes to evaluate include other publicly reported healthcare-associated infections such as catheter-associated urinary tract infections (CAUTI), hospital-onset (HO) methicillin-resistant Staphylococcus aureus bacteremia, and HO Clostridioides difficile infection. It is noteworthy that we have not seen increases in CAUTI for a large system with the early waves of the pandemic, ^{Reference Fakih, Bufalino and Sturm7} underscoring the importance of evaluating multiple measures to assess hospital resilience. In addition, noninfectious measures such as risk-adjusted mortality may be important to study as global measures to assess hospital resilience in response to pandemics or other stressors. ^{Reference Fakih, Ottenbacher and Yehia8}

The pandemic has hastened the need to closely review the structures and processes that influence resilience at the frontline, organizational, and national levels. At the frontline or individual level, it is important to establish process and outcome measures that accurately determine healthcare worker competencies, wellbeing, and their adaptability to change. ^{Reference Ambrose, Catchpole, Evans, Nemeth, Layne and Nichols9} Moreover, interventions to reduce the risk for burnout are essential to our readiness to confront future major stressors. ^{Reference Cohen, Pignata, Bezak, Tie and Childs10} At the organizational level, resilience is supported by investing in a highly reliable culture and processes and making sure that the structures built do not degrade over time. ^{Reference Weick11,Reference Chassin and Loeb12} Organizations play a pivotal role in building capacity for healthcare personnel to function at their optimal performance, taking into account potential stressors that may be encountered. Stressors do not only include patient surges with pandemic waves, but also talent losses and workflow disruptions. Highly reliable organizations identify defects promptly and institute measures to mitigate any gaps or failures. For example, standardization of processes and reducing variation in operational and clinical domains support a better environment for the frontline workers and fewer errors. Supply chain disruptions, more prevalent especially since the pandemic, may have profound impact on both healthcare worker performance and patient care. ^{Reference Katsaliaki, Galetsi and Kumar13} Finally, a psychologically safe environment is an integral component of organizational culture for resilience. ^{Reference Cartland, Green, Kamm, Halfer, Brisk and Wheeler14}

At the state and national levels, our learnings from the pandemic uncovered the important value of public health support to organizations whether providing personal protective equipment, vaccination supply, or other products essential for patient care. However, increased disruptions in supply chain are still occurring post-pandemic (eg commonly used antimicrobial agents, blood culture bottles, sterile fluid), forcing many organizations to institute potentially less than optimal alternative processes. ^{Reference Katsaliaki, Galetsi and Kumar13} National plans to address critical supply chain elements will help reduce disruptive events for organizations and subsequently patient management. On the other hand, national reporting, used to gauge opportunity areas and help identify early stressors that may impact resilience, should be collected with the least burden possible for organizations.

In summary, there is a pressing need to have reliable and actionable process and outcome measures to evaluate resilience in healthcare. Future efforts need to focus on understanding the connection between individual, organizational, and national healthcare resilience measures and building structures to strengthen our readiness for adverse events that we may encounter.