More and more people are reporting that they become constantly ill after surviving a corona infection. A possible cause for this could be an immune system weakened by Covid-19.
For most people, Corona is no longer a big deal because they are vaccinated and/or have already had Covid-19 one or more times. Often the course is even less severe than a common cold. But an infection with SARS-CoV-2 may still be more problematic than expected because it could trigger a long-lasting immune deficiency that makes you susceptible to other diseases.
One indication of this are reports of people who immediately catch a cold after surviving a corona infection or even become ill several times in a row. The explanation for this is possibly an immune deficiency caused by SARS-CoV-2, which could possibly last for several months.
“After infection, the immune system is more receptive to other viral diseases,” the Viennese immunologist Eva Untersmayr-Elsenhuber recently told the “Wiener Zeitung“Anyone who becomes infected with a serious illness after Covid-19, such as a pneumococcal infection or measles, could even have to struggle with an immune deficiency for months because the antibodies, specifically the B cells, remain reduced.
Long-term changes even if the course is mild
A study led by her colleague Winfried Pickl from the University of Vienna confirms this assessment. The work published in the journal “Allergy” shows one Announcement from the university According to him, “even with a mild course, Covid-19 leads to considerable long-term changes in the immune system.”
For the study, the research team examined relevant immune parameters of 133 people who had Covid-19 and recovered. They did the same for 98 people without a corona infection. Nobody was vaccinated because there was no Covid-19 vaccine when the research started in 2020.
In those who had recovered, both the number and composition of various immune cells were analyzed ten weeks and ten months after their illness. In addition, Pickl and his team evaluated growth factors in the blood, which, among other things, play a crucial role in the regulation of cell growth.
Bone marrow infection?
Unsurprisingly, ten weeks after the infection, those who recovered showed clear signs of immune activation in both the T and B cells, in contrast to the uninfected test subjects, says Pickl. However, the research team was surprised by the results ten months after the illness. “Even after mild courses of the disease, we noticed a significant reduction in immune cells in the blood,” explains Pickl. In addition to a drop in SARS-CoV-2-specific antibodies, the researchers also observed an “astonishing change in growth factors in the blood.”
For those who have recovered from Covid-19, this means that their immune system may no longer react optimally, they conclude. The team cites an infection of the bone marrow, which is the central production site of immune cells, as the probable trigger.
The results are a possible explanation for Long Covid, but also for a particularly high susceptibility to other infectious diseases after a corona infection. However, Pickl points out that further research is needed to confirm the hypothesis.
“Dramatic increase” in other infections
Assumptions and indications that a Covid-19 infection can cause an immune deficiency are not new. They have already been discussed and examined in previous cold seasons. This is what one published in “Sage Journals” suggested last October Study According to the research team, the University Hospital Düsseldorf indicates a “dramatic increase in non-Covid-related upper respiratory tract infections (URTI) in all demographic subgroups in Germany, which is associated with enormous effects on socio-economic variables such as the frequency or duration of sick leave.”
To do this, the scientists evaluated electronic medical records from a large German database, which includes a total of 1,403,907 patients from 947 general practitioners and 175 pediatricians’ practices who suffered from an upper respiratory tract infection (URTI) between January 2019 and December 2022. The most important result of their analysis is “undoubtedly the dramatic and sudden increase in URTI visits after the relaxation of Covid measures in 2022,” the researchers write.
Two possibilities discussed
One reason for this increase could be that a Covid-19 infection is a risk factor for later infection with other respiratory viruses, according to the authors of the study. This has not yet been scientifically proven, but other research has come to similar results. They explicitly name one Study from Case Western Reserve University from November 2022. By evaluating a large US database, it found that almost 19 percent of small children were infected with the respiratory syncytial virus (RSV) after a corona infection, while only those who were not infected were infected were around ten percent.
The Düsseldorf researchers also believe it is possible that because of the Corona measures, people had too little contact with pathogens to “train” their immune system sufficiently. However, this hypothesis “has often appeared in the daily press, but not in the scientific literature and is still considered unproven.”
Immune system does not need training, but refreshment
“The immune system is not like a muscle that – if you don’t need it for a long time – would somehow function less well,” said Carsten Watzl in December 2022 WDR. He is Secretary General of the German Society for Immunology. However, part of the immune system needs boosters to protect against certain pathogens, according to the specialist.
“The fact is that with some infections or some pathogens we have to regularly refresh our immunity and then we are protected again for a few years.” Because this didn’t happen for many people, “we now have double or triple the number of people who are currently refreshing their immunity.”
SARS-CoV-2 is not a destroyer
It must also be noted that not only Covid-19, but also other serious viral infections weaken the immune system. To put it very simply, the body can only produce a certain amount of immune cells that react specifically in the event of an infection and are therefore not effective against other pathogens. Depending on the age of the patient and the severity of the disease, weeks or months can pass until there are enough naive immune cells in the blood again that can adapt to new attackers.
Covid-19 would certainly not destroy the immune system like HIV, said the Viennese molecular biologist Sylvia Kerschbaum-Gruber of the Austrian newspaper “The standard“If this were the case, there would be no hybrid immunity from vaccination and infection that best protects against severe disease.
Emanuel Wyler from the Berlin Max Delbrück Center for Molecular Medicine sees an exhausting effect from SARS-CoV-2, but estimates it to be low. “On a scale where a rhinovirus does little to no damage to the immune system and HIV completely destroys it, I would put SARS-CoV-2 – now that most people have been vaccinated against the virus, recovered from it or both – somewhere in that “Locate it in the middle,” he told the science magazine “Spektrum.de“.
