Hospital-onset COVID-19 surged after end of universal screening, masking
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Key takeaways:
- There was a 140% increase in hospital-onset COVID-19 during the transition from pre-omicron variants to omicron.
- A 110% increase in cases was observed between the start of omicron and when hospitals ended universal testing and masking.
HOUSTON — Ending universal masking and admission testing of all hospitalized patients was associated with an increase in hospital-onset COVID-19 at five Massachusetts hospitals, researchers found.
“What prompted the study was our published viewpoints that the use of universal masking and testing continues to have value in hospitals where there is a high concentration of vulnerable patients during times of substantial respiratory virus transmission,” Theodore R. Pak, MD, PhD, an infectious diseases fellow at Massachusetts General Hospital, told Healio.
“As you may know, most U.S. hospitals have stopped these practices and there is little sign that they would ever be restarted, and many made no changes during this past 2023-2024 flu/COVID/respiratory syncytial virus (RSV) season,” he said.
Previously, Pak and colleagues published a study in JAMA Internal Medicine — which was also presented at the 2023 Society for Healthcare Epidemiology of America (SHEA) Spring conference — analyzing data out of the United Kingdom showing an increase in hospital-onset COVID-19 relative to community infection rates immediately after universal admission testing ended in England (32%) and Scotland (73%).
During May of 2023, Massachusetts General Brigham made the policy decision to stop both universal admission screening and masking.
“We thought this could be an opportunity to do a similar study in a population where we had detailed clinical data on the involved cases and could therefore address some analytical concerns raised in response to our JAMA Internal Medicine study as to whether misclassification of hospital-onset cases was inflated by the change in testing policy,” Pak said.
The researchers conducted a retrospective study of all patients admitted to five hospitals between March 6, 2020, and Dec. 14, 2023. Then they identified hospital-onset SARS-CoV-2 infections, which were diagnosed using newly positive SARS-CoV-2 PCR tests 4 days or more after arrival, and community-onset infections, which were diagnosed using newly positive PCR tests 4 days or sooner after arrival.
Using these data, the researchers calculated weekly ratios between hospital-onset and community-onset SARS-CoV-2 cases to account for changes in community SARS-CoV-2 incidence over time.
The researchers split the data into three time periods, comparing changes across the three periods:: pre-omicron period with universal testing and masking in place (March 6, 2020-Dec. 16, 2021), the omicron period with universal testing and masking in place (Dec. 17, 2021-May 11, 2023), and the omicron period without universal testing and masking (May 12, 2023-Dec. 14, 2023).
Throughout the study, which was presented at the 2024 SHEA Spring Conference, there were a total of 626,908 patient admissions, including 24,980 with community-onset COVID-19 and 1,510 with hospital-onset COVID-19.
According to the data, the mean weekly ratio of new hospital-onset to community-onset SARS-CoV-2 infections rose from 2.6% before omicron, to 8.5% (95% CI, 7%-9.9%) during omicron, to 17% (95% CI, 15%-19%) after universal admission testing and masking ended.
The researchers found that there was a significant in case levels after the pre-omicron-to-omicron transition (140% relative increase; 95% CI, 40%-240%) and another significant increase in case levels after universal admission testing and masking ended (110% relative increase; 95% CI, 73-150%).
According to Pak, they also performed chart reviews of a random sample of 100 hospital-onset cases following the policy change. Through this examination, they found features consistent with “true hospital-onset” cases for 97% of these patients, including either new symptoms that had prompted testing, a known COVID-19 exposure in-hospital, or a low PCR cycle threshold value suggesting high viral load rather than prolonged shedding after a prior infection.
Pak explained that this means that prior concerns about misclassification of hospital-onset COVID-19 did not hold up after examining Massachusetts General Brigham cases over a similar change in testing policy.
“We would argue that the potential mechanisms for this increase in hospital onset infections include increases in in-hospital transmission rates that are associated with the end of universal admission testing and masking,” he said.
Pak concluded, “As evidence mounts about the continued impact of hospital-onset respiratory viruses (both in terms of frequency and outcomes), given what we've learned about the efficacy of testing and masking for infection control during the waves of the COVID pandemic and the findings of this study, we would be remiss not to consider the value of these measures during either the next winter or any other future period with high respiratory virus transmission.”
References:
- Pak TR, et al. Abstract 219. Presented at: Society for Healthcare Epidemiology of America Spring Conference; April 16-19; Houston.
- Pak TR et al. Association between stopping universal SARS-CoV-2 admission testing and hospital-onset SARS-CoV-2 in England and Scotland. Presented at: Society for Healthcare Epidemiology of America Spring Meeting; April 11-14, 2023; Seattle.
- Pak TR, et al. JAMA Intern Med. 2023;doi:10.1001/jamainternmed.2023.1261.
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Pak TR, et al. Abstract 219. Presented at: Society for Healthcare Epidemiology of America Spring Conference; April 16-19; Houston.
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