innate, adaptive and booster immunity

How does the immune system in front of vaccine and to illness? Is the protection induced by disease infection really stronger and more lasting than that induced by the vaccine? A third or fourth dose of the severe disease vaccine Covid after a few months from the previous one they can weaken the immune system? In the era of widespread medicine, in which the Sars-CoV-2 coronavirus pandemic has seen many ordinary citizens interested in scientific issues, the immune system, the main ally of our health and our life, has returned to the center of the debate. Between no vax, perhaps vax and yes vax the nuances are the most diverse. And it is good to take stock of what is known to date based on the data. Starting from how the immune system works.

Immune system: innate immunity –

It may surprise, but the outpost of the immune system consists of the skin, give her mucous membranes, from sweat, from mucus, from sebum. These physical barriers are the first filter between us and external, potentially pathogenic agents. Going beyond the skin, immunities can be of two types: theinnate or non-specific immunity eladaptive or specific immunity. “The immune system it is the result of the evolution of hundreds of thousands of years. After the defense barriers such as the skin, the organism has equipped itself with specialized cells that eat germs, and they always do it in the same way: if they encounter a substance or something that is perceived as dangerous they try to destroy it, mostly ‘ eating it ‘. These cells represent the innate immune system “, explains to Official Active Professor Lorenzo Dagna, head of Immunology, Rheumatology, Allergology and Rare Diseases at the IRCCS San Raffaele Hospital in Milan and associate professor of Internal Medicine at the Vita-Salute San Raffaele University. “In the case, for example, in which we get a scratch and a bacterium penetrates under the skin, thus overcoming the first external barrier, the cells of the innate immune system and try to destroy it. It is a very rapid and non-specific immune response, valid immediately for everything we come into contact with ”, emphasizes the immunologist. But the unspecific nature of the innate immune response is not total: “It was once thought to be. The latest data, however, show that evolution has led to an innate immunity that ‘learns’, so to speak, albeit in a less sophisticated way than adaptive immunity ”.

Immune system: adaptive immunity –

But to make the difference between innate and adaptive immunity it’s not just the specificity of the answer. An important role is played by the memory. “After the first answer given by innate immunity, we have that ofadaptive immunity, which is hyperspecific against the bacterium, the virus or in general the pathogen responsible for the attack. And this second immunity has a fundamental characteristic: it is endowed with memory – underlines Professor Dagna -. So when we meet the same antigen again, the immune response will not arrive in weeks, but in a few days “.

The importance of memory cells for the immune response –

Right there memory of the immune system is the one on which i vaccineswhich stimulate a response to the infection in order to make the immune system how to react in the event of an attack by the same virus. “While when we first encounter a substance we have to develop specific cells against it, at the second encounter these cells will already be present in the immune system as memory cells and they will still have the information for the response to this antigen. Consequently, our immune system will already be prepared for defense – explains Dagna -. There immunological memory is exploited by vaccines. The antigen is administered which causes the immune reaction but which is unable to cause disease, although the substance administered is very similar to that which causes disease. In this way it is possible to trigger protection from the disease without giving its effects ”.

Why disease infection gives a stronger response than vaccine infection (but not always convenient) –

It must be said to be honest that if the vaccine is able to ‘teach’ our body the immune response to an infection, it may be less strong than the immune response triggered by illness. “It is very likely that a natural infection can give a more important memory response than that generated by a vaccine. Unfortunately, this is no guarantee of long-term protection. For example, several data suggest that at least in some individuals who have become ill with Covid over time we are witnessing a slow but progressive loss of protective immunity against the virus same. And the same phenomenon was also observed in vaccinated subjects. This in spite of what is observed in other diseases, where once the vaccine or disease you are protected forever or at least for several years ”, explains Professor Dagna.

Immune system, vaccine and booster –

Hence the need for boosters for the vaccine against severe forms of Covid. And some might argue: at this point why is it necessary to get vaccinated, if vaccination does not give protection that is lasting? “A single dose of vaccine it may not be enough to protect us from one reinfection in analogy to the fact that it is possible to get sick again after contracting Covid – recalls the immunologist -. This happens because in such subjects the virus (or the vaccine) was unable to generate a lasting response. Administer multiple doses of vaccinewhile not eliminating the risk of reinfection, it lowers the risk of developing severe illness. Not getting vaccinated exposes you to the risk of getting sick (or getting sick again) of the natural disease, associated with extraordinarily higher risks (even in the case of a second infection) than those associated with vaccination “.

Vaccine against Covid: how often is the recall? –

“As a principle, the vaccinations they all work in the same way, but the duration of protection – explains Professor Dagna – depends from vaccine to vaccine and on the type of immune response that is evoked. In the case of Covid vaccines it has been found that one or two doses, especially in fragile subjects, are insufficient to guarantee protection of adequate duration. For this reason, it was necessary to administer one third dose, or booster, which is of crucial importance especially in frail, elderly or immunocompromised patients. To date, on the contrary, as they also claim WHO and Ema – underlines Professor Dagna – there are no data to support the usefulness of a further one fourth dose of vaccine in the general population, while it is being evaluated whether it might make sense in fragile populations. It is important to remember that there are no data that indicate a possible danger of repeated and frequent vaccinations, but if a general benefit linked to this practice is not demonstrated, it will make no sense to propose it. I remember that there are parts of the world, such as in Africa, which are still awaiting the first dose of vaccine and perhaps our attention should also be directed to these people ”.