After Scotland and England dropped requiring hospitals to test all admitted patients for COVID-19 in 2022, hospital-onset cases outstripped those in the community, according to a research letter published today in JAMA Internal Medicine.
Harvard Medical School researchers conducted a time-series analysis using weekly hospital-onset COVID-19 case counts from Public Health Scotland and the National Health Service England from July 1, 2021, to December 16, 2022. Community-onset cases were estimated using near-weekly household data from the UK Office for National Statistics COVID-19 Infection Survey for the same period.
England and Scotland stopped mandating COVID-19 testing of all admitted hospital patients beginning August 31 and September 28, 2022, respectively.
"Since two-thirds of SARS-CoV-2 transmissions are from people with asymptomatic or presymptomatic infections, transmission risk between patients sharing rooms is high, and universal medical masks can reduce but not eliminate transmission," the study authors wrote. "However, the utility of universal admission testing has been questioned due to resource constraints, care delays, and sparse data demonstrating it reduces nosocomial infections."
41% relative increase in Scotland
During the study period, officials confirmed 46,517 COVID-related admissions (34,183 community-onset and 2,334 hospital-onset) in Scotland, and 518,379 (398,264 community-onset, 120,115 hospital-onset) cases in England.
Average weekly new hospital-onset infections per 1,000 community infections in Scotland rose from 0.78 during the SARS-CoV-2 Delta variant surge to 0.99 during the Omicron wave to 1.64 after mandatory admission testing ended. The immediate level change after universal admission testing stopped was statistically significant (41% relative increase) but not after the transition from Delta to Omicron predominance.
Similarly, during the same periods in England, average weekly new hospital-onset cases per 1,000 community infections climbed from 0.64 during Delta to 1.00 amid Omicron to 1.39 after the testing requirement ended. The immediate level change after universal admission testing ended was statistically significant (26% relative increase) but not after Omicron became dominant over Delta.
Hospitals should exercise caution before stopping universal admission testing for SARS-CoV-2 infections.
The researchers said that the link between ending the universal testing requirement and more hospital-onset than community-onset COVID-19 cases could have been due to patients with unrecognized infection on admission who then spread the virus to other patients and healthcare workers.
The study was limited by its before-and-after design with no concurrent controls and potential spurious associations if policy compliance were minimal or delayed, they said.
"Nosocomial SARS-CoV-2 Omicron infections remain common, with crude mortality estimates ranging from 3% to 13%," they wrote. "Hospitals should exercise caution before stopping universal admission testing for SARS-CoV-2 infections."