The Covid restrictions in Germany have largely fallen. The new legal framework only provides for “basic protection measures”. Modeler Kai Nagel explains what this could mean for the further course of infection. Three factors are relevant to this.

Summer is here – and with it freedom after a phase of almost two years of distance regulations and protective measures. Since the Bundestag and Bundesrat approved the new Infection Protection Act, there have only been a few measures in public life, such as the obligation to wear masks on buses and trains. The corona numbers are still falling.

But will the situation still be as relaxed in autumn? What can we expect as winter approaches again? In an interview with the RND, Kai Nagel talks about the further development of the pandemic. Nagel is a professor of transport system planning at the Technical University of Berlin and has been modeling the spread of the corona virus since the beginning of the pandemic. He has advised the federal government and is considered one of the leading modelers in Germany. “So far everything indicates that there will be another wave of infections. If we’re lucky, this wave won’t come until autumn. If we’re unlucky, she’ll come in the summer,” he explains.

According to Nagel, how the corona situation develops depends on three factors:

As the expert explains, the further development of the corona situation in Germany depends primarily on the evolution of the corona virus. Since the number of infections worldwide is currently still very high, there are enough options for the virus to develop further. Easily transmissible virus variants, which are currently increasingly developing, are problematic.

Kai Nagel (55) is a doctor of theoretical physics and head of the Department of Transport System Planning and Transport Telematics at the Technical University of Berlin. Together with a colleague, he developed a well-known model for predicting traffic density, traffic flow or sudden traffic jams, the Nagel-Schreckenberg model. With the help of a simulation model based on mobile phone data, he has been investigating how the corona virus spreads in private and public spaces since the beginning of the pandemic. He regularly creates simulation models for various pandemic scenarios for the federal government.

In addition, the severity of the disease is of great importance – i.e. the number of people who become seriously ill as a result of an infection and who have to be treated in hospital, for example. As a last point, Nagel mentions the immunity of the population – i.e. the existing protection against infection through vaccination or recovery. Vaccination protects against a severe course, but not against a general infection. As a result, Nagel predicts that another wave of infections may occur in the near future.

The expert estimates the course of a possible new wave of infection to be similar to that of the omicron wave. When it begins depends on when a new virus variant becomes established in society, explains Nagel at the RND. “With BA.4 and BA.5, two variants have already been detected in Germany that appear to be more transferrable. The good news is, your holdings aren’t growing very much; So far, BA.4 and BA.5 account for less than two percent of the positive corona samples. ”But this could look different in two weeks.

Nagel models three scenarios with different virus variants for the upcoming Corona autumn:

Scenario 1: Dominate Omicron or a very similar variant.

If omicron or a similar virus variant remained dominant, this would be the most benign scenario. The existing immunity of the population would remain effective, which is why there would only be a new wave of infections in autumn or winter, according to Nagel. This would be very similar to the wave of infections in spring 2022.

Scenario 2: A more immune-volatile variant that makes you just as sick as Omicron prevails.

If a comparable, more immune-volatile variant were to emerge and prevail, the lower immunity would lead to more corona-related sick leave than during the omicron wave, says the modeler. However, the expert also considers the burden on hospitals and intensive care units to be manageable.

3. An immune-volatile virus variant appears, which again makes sicker than omicron.

“In this scenario, higher incidences than with Omicron and a significantly higher load on the intensive care units could coincide. Even an overload of the health system could not be ruled out if no countermeasures were taken,” warns Nagel at the RND.

As Nagel goes on to explain, we would need to be prepared for all scenarios. Although the third scenario tends to be rather unlikely, since two parameters – transmissibility and disease severity – would have to increase simultaneously, it cannot be ruled out. “But we should expect that restrictions could make sense again.”

The population immunity that has been built up helps to reduce the risk of infections and serious illnesses. However, due to the immune-volatile virus variant, which currently dominates with omicron, population immunity is no longer as effective as before.

The expert explains the problem in the third scenario: In order to prevent the healthcare system from being overloaded without countermeasures, an effective omicron vaccine and a vaccination rate of 100 percent for all people aged five and over would be necessary – a “utopian goal”, according to Nagel.

Modeling of the future course of the corona pandemic is repeatedly being critically questioned. This is mainly due to the fact that many parameters are still imprecise – a high number of unreported corona cases and ambiguities regarding the effectiveness of the vaccine against new variants influence the course of the number of infections, for example. So how exactly can developments be forecast months in advance?

Nagel explains that although the model has become significantly more complex since the beginning of the pandemic, it is still primarily based on estimates. Each sequence of vaccinations and infections leads to a different immunity to the different virus variants. “And of course we don’t know how well this immunity will help against future virus variants, we can only estimate it within plausible ranges and calculate different scenarios based on that,” says Nagel.

“We should prepare for all eventualities so that we can react quickly. And we should keep a close eye on the development of the number of cases: With all previous virus variants, we have seen that their proportion was initially very small, but then increased rapidly from week to week. That means there was always a certain amount of lead time,” summarizes Nagel at the end of the interview. “So good monitoring systems, more sequencing, more capacity in the laboratories are needed to determine this lead time and then to react to the infection situation with appropriate measures We shouldn’t close our eyes and think: It’s all over now, it’s the third year with Corona, countermeasures are no longer needed.”