pandemic
Corona numbers are increasing rapidly – how high is the number of unreported cases?
Test results of corona rapid tests: The incidence in Germany has reached record levels again after almost two years in the corona pandemic. The number of unreported cases is likely to be high. Photo: Jens Kalaene / dpa-Zentralbidl / dpa
© dpa-infocom GmbH
After almost two years of the corona pandemic, the incidence has once again reached record levels. This is only the number of known cases – keyword dark figure. How scientists assess the situation.
Even if the corona numbers skyrocket – the actual incidence is likely to be significantly higher than the reported one. Some researchers assume that around half of infections are currently undetected.
The number of unreported cases is roughly the same as the number of known cases. And as the number of infections rises, the proportion of unreported cases also increases as a rule. So there are even more undiscovered cases compared to the detected infections.
In his calculations, Jan Fuhrmann from the Institute for Applied Mathematics at Heidelberg University assumes that fewer infections are detected in vaccinated people than in unvaccinated people. “This is because, firstly, vaccinated people rarely need a negative test, secondly, they more often have an almost asymptomatic course of the disease, and thirdly, they are often misjudged that they could no longer become infected thanks to the vaccination,” explained the expert in mathematical epidemiology.
What contribution the week-long elimination of free citizen tests made to the number of unreported cases is difficult to estimate. “However, when the citizen tests were introduced, it was argued that only a very small proportion of the cases discovered were due to these tests,” said Fuhrmann. “Conversely, their elimination would not have a major impact, especially since the number of unreported cases among those vaccinated should remain largely unaffected.” He assumes that around half of the actual new infections are currently being discovered.
This is also what Viola Priesemann from the Max Planck Institute for Dynamics and Self-Organization in Göttingen assumes. However, she explains: “The exact value of the number of unreported cases is not relevant for predicting the hospital load and for estimating the trend – as long as it does not change suddenly and significantly.” In order to be able to assess the pandemic – and depending on it, suitable countermeasures – there are incidence, hospitalization and the occupancy of the intensive care units. “That is sufficient to assess the dynamics.” The incidence is still a very helpful indicator. “You can see the extremely sharp increase in the incidence. The intensive occupancy follows a little more smoothly. “
Hajo Zeeb from the Leibniz Institute for Prevention Research and Epidemiology in Bremen assumes that the number of unreported cases will not only increase due to lower test obligations. “But also because vaccinated people and genesis are certainly less tested overall and also have proportionally less severe symptoms and are therefore less likely to be recognized as infected,” he explained. According to Fuhrmann, a higher number of unreported cases means “that contact tracking in particular can make an ever smaller contribution to controlling the epidemic”.
In addition to the incidence, the proportion of positive corona tests in Germany also increased in a weekly comparison. The so-called positive rate has risen from 12.4 to 16.2 percent (first week of November), the Association of Accredited Laboratories in Medicine (ALM) announced last week. “The infection rate in Germany is increasing dramatically,” it said. According to the Robert Koch Institute (RKI), low rates mean that tests are carried out very sensitively and that people with mild symptoms are also recorded. A higher rate therefore also has an impact on the number of unreported cases. According to the ALM, the total number of tests increased only slightly compared to the previous week, to around 1.1 million.
In any case, the researchers point to the great importance of vaccinations in the pandemic, also with a view to other countries: With vaccination rates well over 80 percent as in Portugal, the numbers of infections and treatments are low and very manageable, according to Zeeb. But even then, immunity will decrease.
Increasing vaccination protection remains an ongoing task for the time being, emphasized Zeeb. «The booster vaccinations catapult the vaccination protection significantly upwards again, the effectiveness of the protection against a severe course is, according to available data, even higher than that shortly after the second vaccination, and the protection against infection and transmission of an infection is very pronounced and significantly better than with Vaccinated without the booster. “
Priesemann referred to Israel. There it was possible in the summer to stop the wave with a vaccination rate similar to that in Germany, as around 50 percent of people received a booster vaccination. The third vaccination is important because the immune protection diminishes over time. As a result, in contrast to just two vaccinations, it also brings more protection and depresses hospitalization. In Israel, the third vaccination had a very strong effect on the protective effect in all age groups. “The effect might not be as strong in Germany because the first vaccination interval was longer and the vaccinations were not that long ago as in Israel,” she explained. “But we also expect a clear effect here.”