Fraunhofer ITWM versus Corona: Interview with Dr. Jan Mohring

Using Rapid Testing to Get Out of Lockdown?

Presseinformation / March 29, 2021

Can tests really be effective to reduce the reproduction rate of Covid-19? In addition to vaccination and contact restrictions, the now expanded testing options in Germany are considered an important component of the strategy in the fight against the pandemic. Fraunhofer ITWM scientists have modeled in a paper how no-cause mass rapid testing with subsequent tracking can provide at least as much leverage as contact restrictions to lower the reproduction rate. Three questions to researcher Dr. Jan Mohring, who was in charge of the research paper, that was made to support decision-makers in planning their measures with its modeling and simulations in the SEEvacs project at Fraunhofer ITWM. SEEvacs is a successor project to EpideMSE.

All citizens are entitled to one free rapid test per week. Schools and daycare centers will also soon be conducting regular rapid tests in Germany. How does this contribute to getting out of the lockdown?

Every rapid test that comes back positive and leads to a quarantine helps prevent the Covid 19 virus from spreading. So the more often testing is done, the more infections are detected and people can take early steps to ensure they don't infect anyone else. The current focus in the fight against Covid-19 is on contact restrictions and vaccination. Rapid testing is currently perceived by the public as a way to make their contacts safer. However, random mass rapid testing with subsequent follow-up offers at least as much leverage as contact restrictions to reduce the rate of covid-19 replication: for this, we derived a formula that relates the replication rate to testing, detection, and follow-up rates.

How many rapid tests would need to be performed to lower the R-value?
To do this, we derived a simple analytic formula to estimate what proportion of the population would need to participate in weekly, no-cause, mass rapid testing to bring the current R-value down to an acceptable target value, assuming the same contact behavior. According to our analysis, about one-fifth of the population needs to be tested weekly to stabilize the R-value from the current level of just over 1.2 to 1.0. To push the R-value to 0.9, one-third would need to be tested.

Why is it important to test people without a cause, even or especially people who have no symptoms at all?

First of all, it is important to consider the individual course of infection. We know from the literature that the viral load reaches its maximum at about the time when the first symptoms appear. At this point, however, an average of 44 Percent of the viral load has already spread! The infectious phase starts already 3 days before. And if symptoms show up, then time passes again until the person decides to take the test and gets an appointment. Furthermore, it is known that people without symptoms also spread the virus to a similar extent as symptomatic people. If people are now tested regularly without symptoms, then on average they will be detected at an earlier stage of their infection and, above all, asymptomatic cases will also be noticed. With an assumed dark figure factor of between 4 and 6, this already makes a lot of difference. Overall, it shows that the reproduction rate falls sharply and linearly with the testing rate.

[Only available in german]

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The paper was written as part of the research project SEEvacs, funded by the (Ministerium für Wissenschaft, Weiterbildung und Kultur Rheinland-Pfalz) Ministry of Science, Further Education and Culture of Rhineland-Palatinate. Read the german paper :

German Paper: Testing and Tracking – Effective Means to Reduce the Reproductive Rate of Covid-19 [ PDF 1.35 MB ]

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Fraunhofer ITWM versus Corona: Interview with Dr. Jan Mohring

Using Rapid Testing to Get Out of Lockdown?

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Dr. Jan Mohring

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Eva Fröhlich