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February 22, 2021
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Study shows benefit of serial testing in nursing home outbreaks

Disclosures: See reports no relevant financial disclosures.
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Modeling showed that serially testing asymptomatic residents and staff in nursing homes could prevent more than 50% of SARS-CoV-2 infections in an outbreak, according to study results published in Clinical Infectious Diseases.

“Rapid response to identified COVID-19 in nursing home staff or residents guided by serial (eg, weekly or more frequent) facilitywide testing can be a highly effective approach to controlling COVID-19. In comparison, regularly testing all staff in facilities without known COVID-19 provided a small additional benefit,” Isaac See, MD, a member of the CDC’s COVID-19 Response Team, told Healio.

serial covid testing
Source: See I, et al. Clin Infect Dis. 2021;doi:10.1093/cid/ciab110.

“This analysis was originally undertaken long before vaccination and during a time when testing resources were very limited,” See said. “When testing is limited, those resources should be prioritized first for symptomatic persons, then for outbreak response, and then last for regular testing of staff outside the context of an outbreak.”

Using published SARS-CoV-2 transmission data, See and colleagues used mathematical modeling to determine the percentage of SARS-CoV-2 cases that were prevented if outbreak testing alone or outbreak testing and non-outbreak testing was implemented in nursing homes. They also estimated the effect of simultaneous decreases in the efficacy of isolating infected patients when testing strategies were instituted.

The researchers found that outbreak testing had the potential to prevent between 54% and 92% of SARS-CoV-2 infections with weekly testing and a 48-hour turnaround or daily testing with immediate results, respectively. With non-outbreak testing added, an additional 8% of cases were prevented, depending on test frequency and turnaround time.

See said that timely identification of infected individuals with or without symptoms, as well as isolation of patients with a positive test, is “critical” for mitigating COVID-19 in nursing homes.

“We don’t know everything about how SARS-CoV-2 behaves, and it seems to continue to change over time,” See said. “We also did not look into the effect that immunity from prior infection or vaccination would have. So, continued work on, for example, describing how new variants behave and how vaccination is changing the dynamics of the COVID-19 pandemic in nursing homes is critical.”