Wondering why you have not been infected with the coronavirus yet, even though you have been near infected? The answer may be that you have a certain type of IgA antibodies. IgA stands for Immunoglobin A.
What is it that prevents some people from becoming infected with covid-19, despite working with patients who have the disease?
– We wanted to investigate partly whether there are health factors that protect against covid-19, and partly how the immune system in healthy people was built up before we received vaccines, says Professor Christine Wennerås at the University of Gothenburg.
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Health workers escaped covid
She and her colleague Kristina Eriksson are behind the study, which also shows that people with respiratory allergies can have better natural protection against the virus.
156 health workers at five emergency rooms in the Gothenburg area participated in the study, which took place at the beginning of the pandemic when infection rates were far higher in Sweden than in Norway.
Common to the health workers who did not become coronary heart disease was that they had a type of IgA antibody that binds to the virus. Thus, they prevent covid-19 from getting through the mucous membrane, and the person avoids getting sick.
Other antibodies do not provide protection
– Every tenth person in the study had a built-in protection in the form of IgA antibodies that bind to the virus. These 10 percent were never infected or sick even though they were unvaccinated and worked with infected people, says Wennerås.
Other studies also show that about one in ten have the specific type of IgA antibodies that protect against covid-19 infection.
Everyone has IgA antibodies, it is a common part of the immune system. However, there are different types of IgA antibodies that bind to different types of viruses and bacteria. Otherwise, the immune system consists of T cells and IgG antibodies, which do not appear to have the same protective effect against covid-19.
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Allergy sufferers are also protected
The study also shows that women and people with respiratory allergies have better natural protection against covid-19.
– Already during the swine flu in 2009, it was seen that people with respiratory allergies seem to be better protected against viruses. But that protection has nothing to do with IgA antibodies, Wennerås explains.
Instead, it is a slightly inflamed respiratory mucosa that makes it more difficult for the coronavirus and other viruses to enter the body.
The study is published in European Journal of Immunology.
Karan Golestani, a specialist in infectious diseases at the Norwegian Institute of Public Health, states that since the coronavirus is a mucosal-associated virus, antibodies that act in the mucous membranes probably play an important role in the immune system’s ability to prevent viral infection.
– It is known that people with IgA deficiency may have an increased frequency of respiratory infections in general, he writes in an email to NTB.
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Blood type can determine
From the start of the pandemic, it was known that factors such as smoking, age and chronic diseases could have a major impact on how seriously ill people become from covid-19. As early as June 2020, researchers also discovered that there was a connection between blood type and the probability of serious illness.
People with blood type 0 had a 30 percent lower chance of becoming seriously ill, while blood types A and AB had an increased risk. This has since been confirmed by other studies.
Why this is so, is not yet fully clarified, according to Golestani.
– But there are several theories, including that those with blood type A lack anti-A antibodies, while blood type 0 has both anti-A and anti-B antibodies, antibodies that could theoretically have a protective effect against SARS-CoV-2, he says.
