Coronavirus immunity: is it possible to get COVID-19 twice?

How does immunity to coronavirus appear?

Our immune system, which protects the body from infection,

consists of two parts. The first is always ready to work and takes effect when any pathogenic bacteria or viruses are found in the body - this is innate immunity, it triggers the body's chemical reaction to destroy infected cells. But such an immune system does not provide protection against coronavirus.

The second type is an adaptive immune response, into itincludes cells that produce special target antibodies to fight a specific type of virus, they can stick to it and stop, as well as T cells that can attack only infected cells with viruses. To create such an immune response takes time - on average about 10 days, for which the body learns to produce the necessary antibodies.

If the adaptive immune response is strong enough,then it can create a fairly long-term protection of the body from a certain type of virus. So a large number of modern vaccines for various diseases work.

A key modern problem with a new type of coronavirus is that it is not known whether a powerful immune response occurs in people who have had COVID-19 with mild symptoms or no symptoms at all.

How long does the immune response last?

Each type of virus has a different time. For example, against measles virus, the body receives immunity for life, and against RSV (respiratory syncytial virus) - for only a few months.

New Sars-CoV-2 Coronavirus Existsnot long enough to establish exactly how long the immunity lasts. However, in their studies, scientists compare it with six other known coronaviruses that can attack humans. Four of them cause mainly symptoms similar to the common cold, therefore, immunity to such viruses is very short-lived. Studies show that some patients who have had these types of coronavirus can be re-infected within a year.

Two more coronaviruses - provoking severeacute respiratory syndrome (Sars) and the Middle East respiratory syndrome (Mers) - cause antibodies that were found in the blood of patients and several years after the disease.

At the same time, a professor of medicine from the UniversityEast England, which is studying the emergence of antibodies to coronavirus, believes that even if immunity to the new virus does arise, it will last no more than a few years. However, re-infection, even in the presence of a small amount of antibodies, can take place almost without symptoms, the scientist believes.

Have there been cases of reinfection?

It is also not completely clear yet. Repeated positive tests for COVID-19 can mean many different things - from poor testing, which led to the discharge of a person from the hospital, ending with a change in the type of tests for others that notice a lower concentration of coronavirus in the blood.

However, there are almost no studies of such cases,since people rarely go to hospitals after recovering from COVID-19. Now in China, people who have already recovered from COVID-19 have been tested for coronavirus, but the results of this study are not yet available.

If I have antibodies, is there immunity?

This, too, unfortunately, is not accurate. The World Health Organization has repeatedly expressed a negative reaction to the initiatives of the authorities of various countries to issue special passports to people who have had COVID-19, removing quarantine restrictions from them.

Recent Chinese studies have shown that from175 patients with COVID-19, 30% had a very low quality of these antibodies, so they will not be able to withstand a new infection. In addition, if the body is protected from a new type of coronavirus, this does not mean that it cannot be its carrier.