Warning of “explosive dynamics” in autumn: Corona modelers demand test strategy for vaccinated people too – knowledge

In view of the accelerated infection rate in the corona pandemic and the increasing incidence of hospitalization, a research group from Berlin has called for a far-reaching test strategy that also targets those who have been vaccinated and those who have recovered. At the same time, it questions the future obligation to pay for rapid antigen tests.

“An effective test strategy for autumn 2021 must include those who have been vaccinated / recovered, as they are still involved in the transmission of the virus, even if they rarely show severe courses,” it says in the new report of the group to the Federal Ministry of Education and Research.

The scientific team headed by mobility researcher Kai Nagel from the Technical University (TU) Berlin includes mathematician Christof Schütte and computer scientist Tim Conrad from the Zuse Institute Berlin (ZIB).

Kai Nagel heads the Department of Traffic System Planning and Traffic Telematics at the TU Berlin.Foto: Marcel Rieser, CC-BY-SA 4.0

Based The group simulated various test strategies on an earlier model, which forecast a fourth wave for the fall and thus rapidly increasing hospital numbers. In doing so, measures should be identified that significantly slow down the dynamic of the infection and can avert “the critical situation”.

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In the report, the group admits that the forecasts from the previous model came true earlier than expected. This is due to the delta variant, it says in the report. The mutation had already become dominant in Germany at the end of June, in particular due to those returning to travel, and due to the high level of infection of this variant, “the exponential growth” started earlier than previously assumed.

At the beginning of September, the total number of people demonstrably infected with the Sars-CoV-2 pathogen in Germany since the beginning of the corona pandemic had risen above the four million mark. According to the latest figures from the Robert Koch Institute (RKI) on Sunday, an average of more than 10,000 people are infected with the corona virus every day.

Three measures to avert pandemics

Overall, the researchers name three measures that they consider helpful in warding off pandemics. First of all, there is a mask requirement in public transport and retail, as well as a 2G rule in indoor areas with high density of people. As a third point, they call for the inclusion of those who have been vaccinated and recovered in a test strategy with regular rapid tests, whereby PCR tests are clearly preferred.

The third point is at the heart of the reflections now published by the group. The modelers explain that an effective test strategy is also aimed at the 2G group, “because vaccinated / convalescent people (GG) are also involved in the transmission of the virus, which creates explosive dynamics, and all of the severe courses that it triggers the non-vaccinated / convalescent (NGG) have to go to hospital almost at the same time ”.

This scenario assumes that “under certain unfavorable circumstances, the hospitals will again become overloaded despite vaccinations”. Scientists admit that this is speculative. In order to prevent such a situation at an early stage, they recommend “in particular to consistently monitor the hospital incidence and its occupancy rate and – if necessary – to take prompt action”.

According to the latest information from the RKI last Friday, the number of corona patients admitted to clinics per 100,000 inhabitants within seven days is 1.83 (previous day: 1.74). A nationwide threshold value from when the situation can be viewed critically is not provided for the incidence of hospitalization, among other things because of large regional differences.

After examining four different simulations with restrictions for unvaccinated people, the researchers basically come to the conclusion that, with a view to the short-term goal of effective pandemic control, there is hardly a way around the group of vaccinated and convalescent people. “Overall, none of the strategies we consider feasible leads to a significant reduction in the R value as long as the strategy only affects the unvaccinated,” the report says. This applies particularly to rapidly increasing numbers of infections.

According to the simulations, a rapid increase in the number of hospitals could require a short-term lowering of the R-value by up to 0.8 – a challenge that can hardly be met in the short term.

The research group therefore examined three further restriction measures, the central point of which is a test strategy involving the 2G group. The team states that such far-reaching strategies are potentially promising. The modelers define the use of “PCR tests instead of antigen tests and a frequency of 2-3 tests per (mobile) resident per week” as “far-reaching”. The researchers always assume restrictions for the unvaccinated, especially in the recreational area, in their deliberations.

Criticism of the abolition of free tests

With a view to these research results, the group of experts asks critically “whether it is expedient in the current phase of the pandemic to make the rapid antigen tests chargeable”. At the beginning of August, Chancellor Angela Merkel and the prime ministers of the federal states agreed to abolish the free corona tests by October 11.

Instead, the modelers advocate maintaining the current testing strategy and encouraging vaccinated and convalescents to test before high-density activities indoors. Finally, they would like “ideally even the inclusion of the more precise PCR tests in the catalog of those tests that can be used free of charge even without cause”.

In order to find out which pandemic-related restrictions are appropriate and as little stressful as possible, the scientists compared the German infection situation with those from other EU countries. There there was “a very similar increase in the number of cases from the beginning of July”. In contrast to Germany, however, “in many of these countries, eg Greece, the Netherlands or Spain, this trend has now been stopped” – through restrictions or increasing vaccination numbers, as in France after the introduction of the health passport.

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