A research group from Berlin has called for a far-reaching testing strategy that also targets vaccinated and recovered patients, in view of the accelerated pace of infection in the Corona pandemic and the rising incidence of hospitalization. At the same time, she questions future mandatory payment for rapid antigen testing.

"An effective testing strategy for the fall of 2021 must include the vaccinated/genetically recovered because, even if they rarely show severe courses, they are nevertheless involved in the transmission of the virus," the group's new report to the German Federal Ministry of Education and Research states.

The scientific team, led by mobility researcher Kai Nagel of the Technical University (TU) Berlin, includes mathematician Christof Schütte and computer scientist Tim Conrad of the Zuse Institute Berlin (ZIB).Based on earlier modeling predicting a fourth wave in the fall and thus rapidly increasing hospital numbers, the group simulated various testing strategies. The aim here was to identify measures that could significantly slow down infection dynamics and avert "the critical situation."

In the report, the Group admits that the forecasts from the previous model had already materialized earlier than expected. This was due to the delta variant, the report says. In particular, the mutation had already become dominant in Germany by the end of June due to rice returnees, and because of the high contagiousness of this variant, "exponential growth" had begun earlier than previously thought.

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

Overall, the researchers name three measures that they consider helpful in the pandemic defense. First, they call for mandatory masks in public transportation and retail stores and a 2G rule indoors with high densities of people. Third, they call for the inclusion of vaccinated and recovered persons in a testing strategy with regular rapid tests, with PCR tests clearly preferred.

The third point is the core element of the considerations now published by the group. The modelers explain that an effective testing strategy thus also targets the 2G group "because the vaccinated/genetically gifted (GG) are also involved in the transmission of the virus, this creates an explosive dynamic, and all severe courses triggered by this, mainly among the non-vaccinated/genetically gifted (NGG), have to be hospitalized almost simultaneously."

This scenario assumes "that under certain adverse circumstances, hospital congestion will again occur despite vaccination." The researchers acknowledge that this is speculative. To prevent such a situation at an early stage, they recommend "consistently monitoring hospital incidence in particular, as well as their occupancy rates, and - if necessary - taking prompt action."

According to recent RKI data released last Friday, the number of corona patients admitted to hospitals per 100,000 population within seven days is 1.83 (previous day: 1.74). A nationwide threshold for when the situation should be considered critical is not provided for hospitalization incidence, in part because of large regional differences.

Basically, after examining four different simulations with restrictions on the unvaccinated, the researchers conclude that with an eye toward the short-term goal of effective pandemic control, there is little way around the vaccinated and recovered group. "Overall, no strategy we consider feasible will lead to a significant reduction in R levels as long as the strategy affects only the unvaccinated," the report states. This is especially true when infection rates are rising rapidly, it said.

According to the simulations, a rapid increase in hospital numbers could necessitate a short-term reduction in the R-value of up to 0.8 - a challenge that would be difficult to meet in the short term.

For this reason, the research group investigated three further restriction measures, the central point of which is a test strategy involving the 2G group. In this regard, the team states that such far-reaching strategies are potentially promising. The modelers define "far-reaching" as the use of "PCR testing rather than antigen testing, and a frequency of 2-3 tests per (mobile) resident per week." Restrictions for the unvaccinated, especially in the recreational sector, are always assumed by the researchers in their considerations.

In view of these research results, the expert group critically questions "whether it is purposeful precisely in the current phase of the pandemic to make the rapid antigen tests chargeable." At the beginning of August, German Chancellor Angela Merkel and the minister presidents of the German states had agreed to abolish the free Corona tests as of October 11.

Instead, the modelers advocate maintaining the current testing strategy and encouraging vaccinated and recovered individuals to test prior to high-density indoor activities. Finally, they would like to see "optimally even the inclusion of the more accurate PCR tests in the catalog of those tests that can be claimed free of charge even without cause".

To determine which pandemic-related restrictions are appropriate and least burdensome, the scientists compared the German infection situation with that of other EU countries. There, there had been "a very similar increase in the number of cases from the beginning of July." However, in contrast to Germany, "in many of these countries, e.g. Greece, the Netherlands or Spain, this trend has meanwhile been stopped again" - through restrictions or also increasing vaccination numbers, as in France after the introduction of the health passport.

Image by Michael Kretzschmar