In the blood of some people who have never come into contact with SARS-CoV-2, there are antibodies to related coronaviruses that can attack it.

A small number of people may have acquired immunity that protects them from infection with SARS-CoV-2, even without prior exposure to the virus. Their antibodies, formed in response to infection with closely related coronaviruses, which cause the common seasonal cold, are able to bind SARS-CoV-2, making the disease easier. This is reported in a new article published in the journal Science.

A large team of British medics examined blood samples collected from children under 16 and adults before the pandemic, as well as in its first months, provided that the donor tested negative for Covid-19. Scientists have compared the antibodies present in this blood with samples from people who have already been ill.

As you might expect, those who had been ill with Covid-19 showed various immunoglobulins that attack the S-protein of the virus. However, some people who had not been in contact with it also had immunoglobulins G (IgG) that bind this protein. Out of a sample of 302 adults, there were 16 such children (five percent), and out of 48 children, 21 (44 percent).

These IgGs are part of the acquired immunity that has emerged in humans following a relatively recent infection with coronaviruses similar to SARS-CoV-2. Such cross-reactive antibodies are not as effective in binding its S-protein as intended for it, but they can significantly affect the course of the disease and the course of the epidemic.

Such IgGs are part of the acquired immunity that has emerged in humans after relatively recent infection with coronaviruses similar to SARS-CoV-2. Cross-reactive antibodies are not as effective in binding its S-protein as intended for it, but they can significantly affect the course of the disease and the course of the epidemic.

This may explain the relative ease with which children are believed to tolerate Covid-19. On the other hand, the connection has not yet been proven at all, but it is known that in some cases the presence of cross-reactive antibodies can, on the contrary, complicate the course of the disease. In particular, they impede the production of immunoglobulins directed specifically against the new virus, although they themselves do not fight it effectively enough.