Mass testing for asymptomatic COVID-19 infection among health care workers at a large Canadian hospital

Abstract

Background: The perceived risk of coronavirus disease 2019 (COVID-19) infection for health care workers (HCWs) is high. Although testing has focused on symptomatic HCWs, asymptomatic testing is considered by some to be an important strategy to limit occupational spread. Evidence on the results of large asymptomatic testing strategies in health care is, however, limited. This study examines the uptake and positivity of COVID-19 testing in a voluntary asymptomatic testing campaign at a large Canadian hospital. Methods: In addition to testing HCWs with symptoms, all asymptomatic staff were offered a COVID-19 test at Trillium Health Partners, a large Ontario hospital, from May 27 to June 15, 2020. Testing was offered in four waves, corresponding to the likelihood of exposure to COVID-19–positive patients. The mass asymptomatic testing campaign was offered when the hospital’s community test positivity rate had declined to 5%. Results: Since March 16, the hospital has tested 51.3% of its 10,143-person workforce at least once. In the asymptomatic testing campaign for HCWs between May 27 and June 15, 27% of clinical and non-clinical staff received testing. No large differences were found in the proportions of clinical HCWs tested by their exposure to COVID-19–positive patients. In this campaign, 0.2% of asymptomatic HCWs tested positive. However, these individuals either had mild symptoms at testing and did not self-identify or became symptomatic after testing. Conclusions: At this large hospital with declining community prevalence, a mass asymptomatic testing campaign of HCWs found they had a very low likelihood of testing positive for COVID-19.

Mass Testing With Contact Tracing Compared to Test and Trace for the Effective Suppression of COVID-19 in the United Kingdom: Systematic Review

“…Three of the studies (8%) were implemented in Japan [ 44 , 47 , 58 ], with a sample size of 7339. Two of the studies (6%) were implemented in Canada [ 49 , 68 ], with an overall sample size of 5204 subjects (one of the studies used a hypothetical sample). Two studies (6%) were implemented in Italy [ 57 , 69 ], with an overall sample of 11,097 subjects.…”

“…The prevalence among asymptomatic populations from 6 studies [ 59 , 62 , 66 , 68 , 74 , 75 ] was 3.4% (189/5500, 95% CI 3%-4%). The prevalence in a mixed population from 17 studies [ 57 , 58 , 60 - 65 , 67 , 69 - 73 , 76 - 78 ] averaged 0.009% (895/9,937,378, 95% CI 0.0%-0.0%) ( Figure 5 ).…”

Testing for COVID-19 during an outbreak within a large UK prison: an evaluation of mass testing to inform outbreak control

“…Outbreaks in prisons can be rapidly contained with effective outbreak management (Wilburn et al, 2021) and testing asymptomatic people to contain outbreaks and reduce further spread ( Lambert and Wilkinson, 2021 , Malloy et al, 2021 ). Mass asymptomatic testing has been implemented in particular contexts and settings, including in China ( Zhou et al, 2021 ) and in establishments with a high risk of transmission such as hospitals ( Reid et al, 2020 ) and schools ( Torjesen, 2021 ). However, mass asymptomatic testing was not available until months after the start of the pandemic, and must consider frequency, the test used, and the accompanying public health measures, as well as balancing these with the disruption to the prison regime, the risk of harm from false negative and positive results, and the financial cost ( Lambert and Wilkinson, 2021 ).…”