Immune deficiency after Covid - what we know and what we don't know

An unusually early flu wave, a strong RSV wave in children, plus many colds and bacterial infections: After the end of many corona protection measures in Germany, one can quickly get the feeling that people were not sick as often as in the past months. And now that a large number of citizens in Germany have already been infected with Sars-CoV-2 once or several times, one hears more often of a possibly longer-lasting immune deficiency after Covid-19. What's it all about?

“It is worrying what we are seeing in people who have had multiple corona infections. Studies now show very clearly that those affected are often dealing with an immune deficiency, the duration of which we do not yet know," Karl Lauterbach, the Federal Minister of Health, recently told the "Rheinische Post". In an earlier version, which attracted some attention, he had spoken of an "immune deficiency that could no longer be cured". Lauterbach then made it clear that there was currently no question of an incurable immune deficiency – and he spoke of an error in the release of the text.

Shortly before the turn of the year, Charité virologist Christian Drosten also spoke about a feared aging of the immune system. In a “Tagesspiegel” interview, he referred to immunological findings: These suggested that the aging of the immune system in children after corona infection was much more advanced than expected. "One can now ask oneself pointedly whether an unvaccinated child after infection might have the immune system of an 80-year-old at 30," said Drosten.

Exactly which data Drosten and Lauterbach refer to cannot be said with absolute certainty. If you ask the Ministry of Health, you are generally referred to the Minister's Twitter profile, where he discusses studies. The findings that Drosten spoke of appear to be unpublished. A scientist who is otherwise always well informed about Covid-19 says that he has not yet seen any data on it and wants to refrain from making assessments.

Of course, some studies are already public that have to do with Sars-CoV-2 and the immune system - including long-term consequences. After Lauterbach's statements, they were diligently shared on social media. Some titles sound worrying. To cite just a few examples, there is impaired immunity to fungal infections, long-term disruption of the peripheral immune system, and impaired function of certain cells.

"Unfortunately, the findings that are available are often overinterpreted," said immunologist Christine Falk from the Hannover Medical School recently in "Zeit Online". They are usually difficult or impossible to interpret for laypeople. Many observations also relate to long-Covid patients. From Falk's point of view, there is "currently no reason for most people to worry that their immune system will work less well after one or more corona infections". And she clarified that Covid-19 is also "not airborne AIDS," as some seem to have claimed. "This is nonsense."

The British immunologist Sheena Cruickshank from the University of Manchester resists. Temporary changes in the immune system after an infection are normal, she recently explained. Even if technical details sound dramatic to laypeople, it has been shown that most people's defenses regain their equilibrium after recovery.

Even in vulnerable patients, only a small proportion remained more than six months after infection - mostly in people who were seriously ill with Covid-19 or who had other underlying health problems. Further studies are necessary for this. "For most people, however, there is no evidence of damage to the immune system after a Covid infection," Cruickshank notes.

There are other aspects to consider as well. Sars-CoV-2 is considered to be particularly well researched compared to many other viruses. "Probably no virus infection passes us by without consequences," said molecular biologist Emanuel Wyler from the Max Delbrück Center for Molecular Medicine in Berlin. HIV is known to be particularly damaging to the immune system — and measles essentially resets the immune system, Wyler said. Rhinoviruses, on the other hand, which cause colds, are comparatively harmless. "The question is where Sars-CoV-2 fits into this broad spectrum and how the virus still stands out in vaccinated people compared to the many viral infections over the course of a lifetime."

Wyler also points out that a number of study results date from before the Covid 19 vaccination. What is reported in it about seriously ill people who were infected with early variants is not automatically transferrable to healthy and vaccinated 20-year-olds in the times of the omicron variant.

Immunologists have been emphasizing for months that the most recent waves of colds are primarily to be seen as catch-up effects. Because during the Corona years, other respiratory pathogens circulated less strongly. If people actually had a weakened immune system across the board, other infections would also have to increase - "such as those with atypical pathogens that do not normally make people sick," said Falk.

According to the immunologist, it is still too early for an overall picture – so everything should not always be translated into a warning or the all-clear. Discussions among professionals are ongoing, she said. Much is provisional.

"Aha! Ten minutes of everyday knowledge" is WELT's knowledge podcast. Every Tuesday and Thursday we answer everyday questions from the field of science. Subscribe to the podcast on Spotify, Apple Podcasts, Deezer, Amazon Music, among others, or directly via RSS feed.