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innate, adaptive and booster immunity

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Update with Professor Lorenzo Dagna, Head of the Immunology, Rheumatology, Allergology and Rare Diseases Department at San Raffaele Hospital in Milan

How the immune system in front of vaccine and to sickness? Is the protection induced by the disease infection really stronger and more durable than that induced by the vaccine? A third or fourth dose of the severe disease vaccine covid after a few months of the previous one, they can weaken the immune system? In the era of generalized medicine, where the Sars-CoV-2 coronavirus pandemic has seen many ordinary citizens take an interest in scientific issues, the immune system, the main ally of our health and our lives, has returned to the center of the debate. Between no vax, maybe vax and yes vax the nuances are the most diverse. And it’s good to take stock of what we know so far based on the data. Starting from how the immune system works.

Immune system: innate immunity –

It may come as a surprise, but the outpost of immune system consists of the the skin, give him mucous membranes, sweat, mucus, sebum. These physical barriers are the first filter between us and potentially pathogenic external agents. Beyond the skin, immunities can be of two types:innate or non-specific immunity headaptive or specific immunity. “The immune system it is the result of the evolution of hundreds of thousands of years. After the defense barriers like the skin, the body has specialized cells that eat germs, and they always do it the same way: if they encounter a substance or something that is perceived as dangerous, they try to destroy it, most often ‘to eat it’. These cells represent the innate immune system, explain to Official asset Professor Lorenzo Dagna, Head of the Department of Immunology, Rheumatology, Allergology and Rare Diseases at IRCCS San Raffaele Hospital in Milan and Associate Professor of Internal Medicine at Vita-Salute San Raffaele University. “In the case, for example, where we receive 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 with which we come into contact”, underlines the immunologist. But the non-specificity of the innate immune response is not total: “We used to believe so. However, the latest data 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 differentiate between innate and adaptive immunity it’s not just the specificity of the response. An important role is played by the Memory. “After the first response given by innate immunity, we have that ofadaptive immunity, Which one is hyperspecific against bacteria, viruses or in general the pathogen responsible for the attack. And this second immunity has a fundamental characteristic: it is endowed with Memory – emphasizes Professor Dagna -. So when we encounter the same antigen again, the immune response will not arrive in weeks, but in days.”

The importance of memory cells for the immune response –

Just there immune system memory 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, on 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 that antigen. Therefore, our immune system will already be prepared for defense – explains Dagna -. The immunological memory is operated by vaccines. One administers the antigen which causes the immune reaction but which is unable to cause the disease, although the substance administered is very similar to that which causes the disease. In this way, it is possible to trigger protection against the disease without giving its effects”.

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

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 sickness. “It is absolutely likely that a natural infection could give a larger memory-like response than that generated by a vaccine. Unfortunately, this is not a guarantee of long-term protection. For example, several data suggest that at least in some people who have become ill with covid over time there is a slow but gradual loss of protective immunity against the virus same. And the same phenomenon was also observed in vaccinated subjects. This despite 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 to vaccine reminders against severe forms of covid. And some will say: at this stage, why should you get vaccinated, if vaccination does not provide long-lasting protection? “A single dose of vaccine it may not be enough to protect us from a reinfection by analogy with the fact that it is possible to fall ill again after having contracted 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 reduces the risk of developing serious illness. Not getting vaccinated puts you at risk of getting sick (or getting sick again) from the natural disease, associated with extraordinarily higher risks (even for a second infection) than those associated with vaccination.”

Covid vaccine: what is the frequency of reminders? –

“As a matter of principle, the vaccines they all work the same way, but the duration of protection – explains Professor Dagna – depends from one vaccine to another and the type of immune response 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 a third dose or booster, which is of crucial importance especially in frail, elderly or immunocompromised patients. To this day, on the contrary, as they also claim WHO and EMA – emphasizes Professor Dagna – there is no data to support the usefulness of any other fourth dose of vaccine in the general population, while we assess whether this could make sense in fragile populations. It is important to remember that no data indicates 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 remind you that there are parts of the world, like in Africa, which are still waiting for the first dose of vaccine and perhaps our attention should also be on these people”.