After experiencing COVID-19, you might become more vulnerable to other infections.
Many individuals have been complaining about persistent illnesses following their recovery from COVID-19. A possible explanation for this could be the weakening of the immune system as a result of the COVID-19 infection itself.
Even though COVID-19 is often less severe than a common cold for those who are vaccinated or have had prior infections, a COVID-19 infection might still pose more problems than initially thought. Its long-term impacts on the immune system could make an individual more susceptible to other diseases.
This is evident in reports of individuals contracting colds soon after recovering from COVID-19 or falling ill multiple times in succession. This could be due to the weakening of the immune system caused by SARS-CoV-2, which can persist for several months.
According to Viennese immunologist Eva Untersmayr-Elsenhuber, "After the infection, the immune system is more susceptible to other viral infections." Those who contract severe diseases such as pneumococcal infection or measles after COVID-19 may have to battle immune weakness for months, as the body produces fewer antibodies, specifically B cells.
A study led by Winfried Pickl at the University of Vienna supports this assessment. Published in the journal "Allergy," the study found that COVID-19 leads to significant long-term changes in the immune system, even in mild cases.
The research team analyzed immune parameters in 133 individuals who had recovered from COVID-19 and 98 individuals who had not been infected. The study was conducted before the availability of COVID-19 vaccines.
Ten weeks and ten months after the illness, the team found clear signs of immune activation in both T and B cells in the recovered individuals compared to the non-infected participants. However, ten months after the illness, the team was surprised to find a clear reduction in immune cells in the blood of the recovered individuals. In addition to a decrease in SARS-CoV-2-specific antibodies, the researchers also observed a "remarkable change in growth factors in the blood."
For COVID-19 survivors, this means that their immune system may not react optimally, the researchers concluded. They suspect an infection of the bone marrow, which is the central production site of immune cells, as the likely cause.
The results could explain long COVID and the individuals' heightened susceptibility to other infectious diseases after a COVID-19 infection. However, further research is needed to confirm the hypothesis.
Rumors and hints suggesting that a COVID-19 infection could cause immune weakness are not new. A study published in "Sage Journals" by the University Clinic Düsseldorf in October 2022 suggested a "dramatic increase in non-Covid-related upper respiratory tract infections (URTI) in all demographic subgroups in Germany, with significant impacts on socio-economic variables such as the frequency or duration of sick leave."
The researchers analyzed electronic medical records from a large German database, covering 1,403,907 patients from 947 general practitioner and 175 pediatric practices who had an URTI between January 2019 and December 2022. The most important finding of the analysis was "undoubtedly the dramatic and sudden increase in URTI visits after the easing of Covid measures in 2022," the researchers wrote.
One possible reason for this increase could be that a COVID-19 infection is a risk factor for subsequent infection with other respiratory viruses, the authors suggested. Although this is not yet scientifically proven, other research comes to similar conclusions. They also considered the possibility that people had too little contact with pathogens due to COVID-19 measures, not allowing their immune system to "train" sufficiently. However, this hypothesis "has been frequently discussed in the daily press, but not in scientific literature and remains unproven."
"The immune system is not like a muscle that would function less well if not used for a long time," said Carsten Watzl, general secretary of the German Society for Immunology, in December 2022. A part of the immune system does need boosting to protect against certain pathogens, however. "It's the case that we have to regularly boost our immunity against some infections or pathogens, and then we're protected 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 boosting their immunity."
Moreover, it should be noted that not only COVID-19, but also other severe viral infections weaken the immune system. In simplified terms, the body can only produce a certain amount of immune cells that specifically react to an infection and are therefore not effective against other pathogens. It can take weeks or months for enough naive immune cells to be present in the blood again, depending on the patient's age and the severity of the illness.
According to Sylvia Kerschbaum-Gruber, a molecular biologist based in Vienna, Covid-19 doesn't decimate the immune system like HIV, as claimed in an article by the Austrian newspaper "Der Standard". If that was indeed the case, hybrid immunity from vaccinations and infections wouldn't offer the strongest shield against severe illness, which is a bonanza for our health.
Emanuel Wyler, from Berlin's Max Delbrück Center for Molecular Medicine, agrees that there's a tiredness effect due to SARS-CoV-2, but maintains it's relatively subdued. He tells science magazine Spektrum.de, on a scale where a rhinovirus barely impacts the immune system and HIV obliterates it, SARS-CoV-2, taking into account current vaccination and recovery rates, can be situated somewhere in the middle.
After recovering from COVID-19, some individuals may experience increased susceptibility to other viral infections such as the flu. This is due to the long-term impacts of COVID-19 on the immune system, which can weaken its ability to fight off other infections effectively.
A study published in "Sage Journals" by the University Clinic Düsseldorf in October 2022 also suggests a significant increase in non-COVID-related upper respiratory tract infections (URTI) in Germany after the easing of COVID-19 measures, which could be linked to the weakening of the immune system following a COVID-19 infection.
