Continued increases in the incidence of healthcare-associated infection (HAI) during the second year of the coronavirus disease 2019 (COVID-19) pandemic

Data from the National Healthcare Safety Network were analyzed to assess the impact of COVID-19 on the incidence of healthcare-associated infections (HAI) during 2021. Standardized infection ratios were significantly higher than those during the prepandemic period, particularly during 2021-Q1 and 2021-Q3. The incidence of HAI was elevated during periods of high COVID-19 hospitalizations.

ventilator days decreased by almost 20% between 2021-Q1 (n = 1,055,497) and 2021-Q2 (n = 849,062). Although encouraging results were seen during this time, SIRs for CLABSI, VAE, and MRSA bacteremia, and device utilization for all 3 devices remained significantly higher than prepandemic values (Table 2 and Supplementary Material online).

Third quarter 2021 (2021-Q3)
Despite decreases in 2021-Q2, a reversal in the direction of SIRs was observed in 2021-Q3. CLABSI, CAUTI, VAE, and MRSA bacteremia SIRs were significantly and substantially higher compared to the SIRs from the prior 2021 quarters and the corresponding prepandemic quarter (Table 3). Particularly, the CLABSI and VAE SIRs of 1.04 and 1.60, respectively, were higher in 2021-Q3 than during any previous quarter since the beginning of 2019. The number of VAEs during 2021-Q3 was 149% higher than the number reported during 2019-Q3 from the same set of hospitals, and the ventilator SUR increased by 40% from 2019-Q3 (SUR, 0.91) to 2021-Q3 (SUR, 1.28).

CDI and SSI
The 2021 CDI SIRs were significantly lower than those from 2019 for all quarters analyzed. Continued decreases in CDI were evident throughout 2021: the SIR for 2021-Q2 was 0.50 and the SIR for Q3 was 0.48, which were lower than those from the prior 2020 and 2021 quarters. For most quarters and procedure types analyzed, no significant changes in SSI incidence were detected.

Discussion
Our analysis revealed elevated incidence of CLABSIs, CAUTIs, VAEs, and MRSA bacteremia infections during 2021, especially during the first and third quarters of the year.
During 2021-Q1, all-time highs of COVID-19-associated hospitalizations were recorded throughout the country. 9 Although large increases were noted in CLABSI, VAE, and MRSA bacteremia in 2021-Q1, the increase in the CAUTI SIR was modest. Improvements in CLABSI, CAUTI, VAE, and MRSA bacteremia SIRs were observed in 2021-Q2, coincident with the dramatic reduction in nationwide COVID-19 hospitalizations. 9 However, as the severe acute respiratory coronavirus virus 2 (SARS-CoV-2) δ (delta) variant emerged in 2021-Q3, dramatic increases in SIRs were observed again. 10 Although data from the SARS-CoV-2 Ο (omicron) variant surge will be forthcoming, SIRs might follow similar trends in 2021-Q4 and early 2022.
Changes in most SIRs were driven by changes in the number of reported HAIs, with several factors contributing to such changes. First, device-associated HAIs were likely affected by the continued alteration of hospital practices that occurred throughout the pandemic. Modifications of CLABSI prevention practices during 2020 are well documented, 3,11 and prevention practices likely continued to be altered during 2021. By contrast, the modest increase in CAUTI SIRs may be related to the fact that catheter removal, a primary approach to CAUTI prevention, was still possible even during times of stress on the healthcare system. Conversely, pandemic-related improvements in hand hygiene, PPE practices, and environmental cleaning may have contributed to the decreases observed in the CDI SIR. Colon surgeries and abdominal hysterectomies were not typically performed as part of COVID-19 care, and process flows in the operating room remained relatively unchanged during this time. 12 This finding may explain the lack of significant changes observed in SSI SIRs.
Second, different patients may have been admitted to healthcare settings in 2021 compared to the prepandemic period, and the increases in SIRs may be explained by changes in the proportion  of patients with different characteristics (eg, race or ethnicity and comorbidities). Although some characteristics (eg, patient location) were controlled for in the device-associated HAI SIRs, the riskadjustment models may not have adjusted for all relevant characteristics. In addition, increases in SIRs could have been due to increased patient morbidity from COVID-19. One 2020 study found that the most common cause of VAEs during surges of COVID-19 was acute respiratory distress syndrome, whereas most VAEs in 2019 were caused by less severe events such as pneumonia. 13 The national SIR for VAE increased the most of all HAIs in 2021, with the greatest increase (60%) occurring during the SARS-CoV-2 δ (delta) variant surge in 2021-Q3. Although a previous analysis found no change in the proportion of adults requiring ventilation during the SARS-CoV-2 δ (delta) variant surge compared to the first half of 2021, 14 the largest increase (40%) in the national ventilator SUR since the start of the pandemic occurred during 2021-Q3. Overall increases in device-associated HAI SIRs, particularly VAE, may reflect an increase in the frequency and duration of device use and an increase in the average length of stay during COVID-19 surges. 1 The limitations of this analysis are similar to those previously reported. 1 The 2021-Q3 results were generated before the HACRP reporting deadline and should be considered preliminary. Hospitals and units that opened during 2020 or 2021 were not included. All HAIs regardless of patient's COVID-19 status were included, and the impact of a COVID-19 diagnosis on the SIRs could not be determined.
For most HAIs, our results are representative of most acute-care hospitals in the United States and provide a national picture of the impact of COVID-19 on HAI incidence. Our findings describe the increases in HAIs that occurred during the 2021 COVID-19 pandemic year and underscore the continued challenges experienced in infection prevention. Resilient approaches are needed to reduce HAIs in 2022 and beyond. 15 Supplementary material. To view supplementary material for this article, please visit https://doi.org/10.1017/ice.2022.116 their continued efforts in HAI surveillance and prevention and for their unwavering commitment to patient safety during the second year of an unprecedented public health emergency. The authors also thank all members of the CDC Division of Healthcare Quality Promotion, who work tirelessly to develop, support, and test the NHSN application and to analyze and disseminate important public health data. They have provided continual education and support to the infection prevention community throughout the COVID-19 pandemic. The findings and conclusions in this article are those of the authors and do not necessarily represent the official position of the US Centers for Disease Control and Prevention.
Financial support. No financial support was provided relevant to this article.