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A new strain of coronavirus Covid-19 has caused panic in the world. However, gradually information about him began to accumulate, he was studied quite well. And now it is already clear how immunity is developed to it. In general, the scheme is the same as for other types of SARS.
With respect to these viruses, a person develops cellular immunity, and re-infection is much less common or easier. But Covid-19 mutates quickly enough, and the body may not have time to adapt to its changes. According to the chief freelance specialist in infectious diseases of the Ministry of Health of the Russian Federation Elena Malinnikova, cases of re-infection with a new type of coronavirus are quite likely. There is evidence that it is possible to infect an already ill person with other variants of the same virus. At the moment, Covid-19 is looking for its niche among other human respiratory diseases, which is why it is changing so quickly.
Initially, humans do not have immunity to this type of coronavirus. Since the infection is unfamiliar to the body, it does not immediately recognize it, so absolutely everyone can get sick.
“However, do not panic – the same scheme works with many other viruses. For example, flu vaccines are made every year because the virus mutates and the old vaccine will no longer work. And even this does not guarantee complete invulnerability – you can still get infected with the flu, but get sick in a milder form, ”says biotechnologist Denis Yudchits.
Against such infections, stable immunity is not formed either after illness or with the help of vaccinations. However, if a person does not have chronic diseases, then he is much more resistant to re-infection with unaltered Covid-19. In the presence of concomitant pathologies (lung diseases, heart disease, reduced immunity), there is a high probability of becoming infected again even with the same virus.
Currently, not a single person has yet been found in the world who is initially protected from coronavirus. Until almost everyone gets sick and collective immunity develops, people will become infected.
Some people are ten times less likely to get sick, but not due to specific immunity to the virus, but simply because of a stronger body. The younger the person, the lower the risk for him. In most cases, in children and young people, coronavirus infection proceeds without any complications.
In older people, the body is weakened, and many chronic diseases worsen the course of the coronavirus. The highest mortality rate is 80%, it is in people over 60 years old. Most initially had serious problems with the lungs and heart.
The principle of immunity to coronavirus is the same as to other similar viruses. The immune system fights for the constancy of the genetic composition of the organism. That is, any foreign genes: bacteria, viruses, cancer cells – our immunity attacks and tries to exterminate.
All people have innate immunity. It reacts immediately to the penetration of microbes and does not form a “memory” for them. Inflammation from a splinter is precisely its manifestation. The next time, innate immunity will react to bacteria in the wound in the same way, without “remembering” how to deal with it and acting on the spot.
Acquired immunity is needed to fight more serious infections where action is required immediately. It develops as a reaction to each individual type of pathogen. This immunity needs time to learn the infection.
The formation of adaptive or acquired immunity is a very interesting and thoughtful mechanism. Each virus or bacterium has antigens – proteins that are located on their surface. They respond to special immune cells – B-lymphocytes. They identify these antigens, check with their “database”, and if it is not a familiar antigen, as in the case of coronavirus, then a chain of successive reactions is launched.
Active production of proteins begins – antibodies that bind to antigens, and this interaction can be compared with the “key – lock” mechanism. Linking, the antibody puts a “label” for other cells of the immune system, a signal for the destruction of the virus or bacteria. Having done its main job, that is, having marked the virus, all information about it is “recorded” and when it is re-infected, the immune system will already know how to respond to the penetration of the infection. And in the blood test, a certain titer of antibodies to the coronavirus is determined.
When enough people develop immunity to an infection, they talk about herd immunity, which also protects those who do not have antibodies to the virus. This will stop the Covid-19 pandemic and return to normal life.
Previously, it was not possible to achieve the goal of “herd immunity”. After all, it was necessary for millions of people to get sick, and this is associated with thousands of deaths. Vaccination against coronavirus is a great opportunity to build herd immunity and overcome the pandemic.
Immunity after vaccination
Vaccinations work on the same principle – a specially weakened virus is introduced into the body, its part, which cannot cause illness. But it is enough for the immune system to study and “remember” it. Therefore, a vaccinated person is less likely to get infected or get sick very easily, his immunity immediately attacks strangers. After certain diseases or vaccination against, for example, measles, immunity remains for life.
All this works if the bacteria or viruses do not change. When they mutate, their antigens change, and antibodies are no longer suitable for them. Immunity again does not “recognize” the causative agent of the disease. Unfortunately, the coronavirus mutates quickly, and this is the main problem. Against such infections, every year it is necessary to develop a new vaccine based on a new strain of the virus, taking into account its changes. Although it is noted that existing vaccines also work against new strains of the virus.
How long does immunity last?
A number of studies show that the highest levels of protective antibodies are in those people who have had a severe infection. And contrary to popular belief, the severity of immunity did not depend on age and gender.
If we talk about duration, then immunity lasts for at least 5-7 months. Perhaps it is for these reasons that re-infection is possible, because enough time has passed for some patients to wear out protective antibodies.
Previously, it was reported that people who had covid-19 easily or as carriers did not have strong immunity. However, a closer examination of the study showed that its data were misinterpreted. And for its low performance, they mistakenly took the neutralization of antibodies that occur in the first time after the disease. After their number stabilizes and persists for a long time.
The fact is that with a typical viral infection, the first wave of immune cells is formed, they produce antibodies, but their life expectancy is short. As a result, the number of antibodies decreases.
But then long-lived cells come into play, which can exist for years and produce antibodies.
Popular questions and answers
Answered popular questions about immunity to coronavirus allergist-immunologist of the highest category, Ph.D.Ksenia Bocharova.