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Corona: Why herd immunity may be impossible – and vaccination still helps

The global vaccination campaigns are raising hopes that the corona pandemic will end soon. But instead of the much-invoked herd immunity, some scientists prefer to speak of the “new normal”. However, this is not a devaluation of the vaccinations, because they still have the potential to take the horror of the pandemic.

According to projections, the pandemic will come to a standstill on its own if enough people are immune, either because they have been vaccinated or because they have become infected. When herd immunity could be achieved depends on how quickly the pathogen spreads. Epidemiologists measure this with the reproduction factor, the famous R-value, which even laypeople are now familiar with. However, this depends on many factors, for example whether more contagious variants spread or whether people adhere to hygiene rules.

Initially, experts assumed that in the case of the new Sars-CoV-2 coronavirus, herd immunity could be achieved if 60 percent of the people in the country are vaccinated. Other estimates are now more likely to be 80 percent.

Free beer with vaccination

The first scientists are already completely deviating from the hope of herd immunity. The data expert Youyang Gu recently renamed his well-known model “The path to herd immunity” to “The path to normality”, reports “Nature”. According to the journal, there are five reasons for doubts about herd immunity:

Study: Vaccinations alone cannot stop a pandemic in the foreseeable future

According to a study recently published in The Lancet Infectious Diseases, a third wave threatens in Great Britain if measures are relaxed too quickly. Vaccinations alone could not push the R-value below 1 according to the model calculations. If all measures were abolished immediately, the value would jump to 1.58. 100 infected people would then infect an average of 158 more people, and the virus would inevitably spread. This could result in 130,000 Covid deaths by January 2024.

The scientists admit that the vaccines could possibly protect better against deaths and serious illnesses than priced into the model calculations. Nevertheless, they recommend loosening corona measures only slowly. In particular, the vaccinations are no substitute for masks, contact tracking and tests.

“Then we breed these escape variants here in Germany.”

The physicist and modeler Viola Priesemann from the Max Planck Institute for Dynamics and Self-Organization also warns of new mutations. “In the worst case, a variant develops that forces us to start again with the vaccination from scratch,” said Priesemann on Wednesday evening on the ARD talk show “Maischberger”.

So-called escape variants developed where many people had already been vaccinated, explained Priesemann. If many have been vaccinated and at the same time there is a high incidence, “then we breed these escape variants here in Germany,” said Priesemann with a view to the upcoming summer. Another reason to keep the number of new infections as low as possible.

So what does the future look like if the vaccinations may not bring herd immunity? Long-term prognoses assume that Covid-19 could become endemic and break out again regularly, similar to the flu. However, this is not necessarily a cause for despair.

Stopping the transmission of the virus is a way to return to normal, said Stefan Bottle, epidemiologist at the London School of Hygiene & Tropical Medicine, the journal Nature. It is time for more realistic expectations. Even if vaccinations should not allow herd immunity, however, they reliably protect people from severe courses and could prevent deaths. The Covid-19 disease may not go away completely, but its omnipotence will likely decrease.

With material from dpa

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