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Screening with rapid tests twice a week can significantly reduce infection in schools and workplaces

A new scientific report prepared for the Statens Serum Institut concludes that systematic use of rapid tests for COVID-19 twice a week at, for example, a workplace or school, could reduce new cases of infection by 36-55%. The conclusions are based on a scenario where rapid tests are assumed to be half as sensitive as traditional PCR tests and that everyone in the group is tested.
Antigen test
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Researchers from Roskilde University's PandemiX Center, together with collaborators at the Niels Bohr Institute at the University of Copenhagen and the University of Southern Denmark, have investigated the epidemiological use of rapid tests (antigen tests with rapid response) for COVID-19. In the report, the researchers focus on using these tests for targeted screenings in defined groups of people.

The researchers developed two mathematical models (a purely statistical model and an individual-based model), which show the effect of repeated screening with antigen tests, including in particular the balance between how often tests are conducted, the sensitivity (the true positive rate) and how much of the group is actually tested. Despite the substantial differences in approach, both mathematical models show that screening in workplaces and schools with antigen testing has the potential to reduce infection rates by 36-55%.

Antigen testing is a useful epidemiological tool in the fight against COVID-19

Antigen tests can be performed on site and provide a quick response but are less sensitive than PCR tests. The positive effect of antigen tests is due to the fact that the lower sensitivity of antigen tests is outweighed by the benefits of frequent tests and a rapid result. The mathematical models assume that people who test positive go into isolation immediately and do not return until they stop posing a risk of infection. The two mathematical models do not take account of the effect of the existing infection detection efforts.

Three models give consistent results

Selected results from the authors' two models are summarized in the table below. Even the most conservative scenario (50% sensitivity and 60% participation) leads to a 22-30% reduction in infection at schools or in the workplace. The most optimistic scenario (70% sensitivity and 100% participation) leads to a 50-60% reduction in new infections. In the table, the two models are compared with new American research conducted by Daniel B. Larremore from the University of Colorado Boulder (et al.), who earlier this year concluded that a high-sensitivity test with a one-day response time (e.g. PCR tests) is less effective than a low-sensitivity test with an immediate response (e.g. antigen tests).


Table showing effect of antigen testing