A four-week “Lockdown Light” has been in effect in Germany since November 2nd. This is to stop the rapid increase in the number of Covid 19 cases. But what happens after that? Using mathematical models developed during the first Covid-19 wave, researchers have now simulated possible scenarios for the further course of the pandemic up to spring 2021. A single lockdown in November is therefore not sufficient to keep the infection rate under control.
In order to slow down the second wave of Covid-19 infections, a “lockdown light” is in place in Germany until the end of November: restaurants and leisure facilities are closed, cultural events are canceled, meetings of more than ten people are prohibited. On the other hand, schools and kindergartens remain open, as do hairdressers and shops. The aim of the measures is to reduce the number of new infections to such an extent that the health authorities can keep up with tracing contacts. In addition, overloading the intensive care units due to too many seriously ill Covid 19 patients should be avoided. Are these measures enough to stop the second wave and prevent a third? Or are further restrictions necessary?
Further development simulated
A team led by Jan Fuhrmann from Forschungszentrum Jülich and Maria Barbarossa from the Frankfurt Institute for Advanced Studies (FIAS) has now investigated this with mathematical simulations. The result of the researchers: If all restrictions were lifted after the four-week lockdown, there would very likely be a third, significantly stronger Covid-19 wave in the course of winter. Further short-term “breakwater lockdowns”, on the other hand, could help to control the number of infections and prevent overloading of the intensive care units. Alternatively, according to the simulations, permanent, less restrictive measures would also be suitable to curb the spread of the virus to such an extent that care for all patients is guaranteed.
“Our long-term scenario models are to be understood qualitatively and do not claim to predict the real course exactly,” says Fuhrmann. “However, the scenarios clearly show how the epidemic would develop under different measures. We emphasize that the number of cases predicted in the simulations, some of which is very high, will only occur if further measures necessary for containment are not taken. That would be, for example, locally limited shutdown periods that have not yet been taken into account in the scenarios. “
Contact rate as a benchmark
The researchers do not recommend specific political measures based on their data. Since a combination of different measures has usually been used up to now, it is difficult to assess the effect of individual measures. Another factor of uncertainty is how the population will react to the number of cases and political guidelines. The researchers therefore base their simulations on contact reductions of different strengths without specifying how these are to be achieved.
They use the late summer of 2020 as a reference value for the contact rate, when the number of cases was low and there were only a few restrictions. The researchers define a limit to 35 percent of these contacts as a “soft shutdown”, a reduction to 25 percent as a “strong shutdown” and a limit of 15 percent as a “severe shutdown”. Even for scenarios without a shutdown, they assume that the contact rate will be reduced to around 60 percent of the late summer value during winter. They classify the current “Lockdown Light” between a “Soft Shutdown” and a “Strong Shutdown”.
November shutdown is not enough
On this basis, the researchers worked out four exemplary scenarios. Without the shutdown in November, the number of new infections in January would have increased to over 100,000 on a seven-day average. At times, up to 35,000 intensive care beds would have been required. According to the DIVI intensive care register, which records the capacity of the German intensive care units, there are currently only around 28,000 beds available, of which around 18,000 are currently occupied by other patients. Around 3,000 Covid-19 patients are currently (as of November 10, 2020) treated in intensive care units nationwide.
The current shutdown can delay the massive increase in infections, but not prevent it, as the researchers’ calculations show. If no further measures are taken, around 70,000 new infections per day can be expected in February and March 2021 and over 20,000 intensive care beds would be needed for Covid 19 patients at times. According to the simulations, this third wave would not end until May 2021.
Further lockdowns or long-term measures
One or two additional “breakwater lockdowns” of two weeks each, on the other hand, could reduce the number of cases considerably. Depending on the timing and strength of the lockdown, the daily number of new infections could be kept below 40,000, with the pandemic wave peaking in February or March. The number of intensive care beds required could remain below 10,000.
According to the researchers, permanent contact restrictions without shutdown are an alternative to short-term, strong restrictions. If implemented consistently, these could also keep the number of intensive care beds required below 10,000. According to the simulations, a combination of long-term measures with short-term shutdowns would be particularly effective.