Results from Canton Grisons of Switzerland suggest repetitive testing reduces SARS-CoV-2 incidence (February–March 2021)

Abstract

In February 2021, in response to emergence of more transmissible SARS-CoV-2 virus variants, the Canton Grisons launched a unique RNA mass testing program targeting the labour force in local businesses. Employees were offered weekly tests free of charge and on a voluntary basis. If tested positive, they were required to self-isolate for ten days and their contacts were subjected to daily testing at work. Thereby, the quarantine of contact persons could be waved.Here, we evaluate the effects of the testing program on the tested cohorts. We examined 121,364 test results from 27,514 participants during February–March 2021. By distinguishing different cohorts of employees, we observe a noticeable decrease in the test positivity rate and a statistically significant reduction in the associated incidence rate over the considered period. The reduction in the latter ranges between 18 and 50%. The variability is partly explained by different exposures to exogenous infection sources (e.g., contacts with visiting tourists or cross-border commuters). Our analysis provides the first empirical evidence that applying repetitive mass testing to a real population over an extended period of time can prevent spread of COVID-19 pandemic. However, to overcome logistic, uptake, and adherence challenges it is important that the program is carefully designed and that disease incursion from the population outside of the program is considered and controlled.

Effectiveness of testing, contact tracing and isolation interventions among the general population on reducing transmission of SARS-CoV-2: a systematic review

“…Both positive and negative impacts of testing on transmission were reported; this may be due to conflicting actions of testing; more testing leads to a higher finding was a reduction in hospitalizations of 25% (35% to 11%) in intervention districts compared to synthetic control. Taken together, these three studies [10,20,77] show the benefits of large-scale testing of the population-especially when infection is relatively common, as in Pavelka et al [10] and Zhang et al [77]. Earlier in the outbreak, when resources were generally more limited, the actions of testing and contact tracing might have been swamped by more stringent control measures such as lockdowns or social distancing.…”

“…Of the 25 studies included, 12 used data from multiple countries across Europe, America, Africa and Asia [56,57,60,63,64,66,[69][70][71][72]75,78]. From the remaining studies, there were nine studies based in Europe, including five from the UK or England [65,67,74,76,77], and one from each of the following countries: Portugal [68]; Spain [61]; Switzerland [20] and Slovakia [10]. Two studies were based in Asia, one from China [58] and one from South Korea [62] and the final two studies were based in Colombia [59,73].…”

“…(ii) Testing strategies (12 papers) Nine papers performed statistical analyses across multiple countries to assess the impact of changing patterns of control [57,63,64,66,[70][71][72]75,78], while three examined testing strategies in single countries [10,20,77]. Many of the cross-country studies used the OxCGRT [83] to inform the type and strength of epidemic controls in each country over time.…”

“…Chan et al [56] Nam et al [69] Malheiro et al [68] Love et al [67] Lopez et al [61] Zhang et al [77] Zamanzadeh & Cavoli [78] Yalaman et al [75] Ssentongo et al [72] Spiliopoulos [71] Pozo-Martin et al [70] Pavelka et al [10] Leffler et al [66] Hong et al [63] Haug et al [64] Gorji et al [20] Chew et al [57] Wymant et al [74] Vecino-Ortiz et al [73] Kendall et al [65] Gianino et al [60] Fetzer et al [76] Fernandez-Nino et al [59] Deng et al [58] contact tracing testing strategies isolation package…”

“…In total, over 4 million tests were performed (out of a total population size of 4.5 million adults), with 50 thousand testing positive; while the impact was spatially and temporally heterogeneous, it was estimated that mass testing led to a 56% reduction in prevalence of infection between the first and second rounds. Gorji et al [20] analysed the impact of weekly testing of employees in the Canton Grisons area of Switzerland during February and March 2021; companies enrolled in the testing scheme saw an 18%, 47% and 50% reduction in incidence in employees across three cohorts (with the latter two values being significant at p < 0.05) for those that had been enrolled for one, two or three weeks compared to newly enrolled companies. The Gorji et al [20] study echoes similar findings where regular testing has been used on specific sectors of the population including school children and healthcare workers.…”