“It’s the third dose that boosts the immune memory”

There is talk of opening vaccination hubs because the possibility of extending the third dose of vaccine is increasingly looming (a booster, as there have been others for other vaccines and as perhaps always will be). About antibody protection, third dose and much more we talked with microbiologist Massimiliano Scutellà, director of the Cardarelli Molecular Biology Laboratory which, in the first instance, reiterated the “fundamental importance of get the vaccine for all those people at risk, such as critically ill patients, the immunosuppressed, the elderly. In short, it is paramount to vaccinate everyone “. Everyone, on all continents, because a pandemic is not won only at certain latitudes. Certainly we cannot save ourselves (in a single region or in a single state), and this should always be kept in mind for ‘functional’ reasons, yes, as well as for ethical reasons.

Today in the Corriere della Sera in an interview with Alberto Mantovani, scientific director of the Humanitas Institute of Milan, expressed his opinion on the third dose. “It should be administered, in the light of what scientific data suggest. And in any case, there are at least three good reasons: to protect myself, my loved ones and the people I come in contact with, especially if I am a healthcare professional “.

Doctor Scutellà, a recent Lancet study that Primonumero also reported a few days ago shows that the ability to become infected and transmit the infection does not differ too much between vaccinated and unvaccinated. We want to clarify if and why it is important to get vaccinated?

“We can get infected even though we are vaccinated and despite having a title of neutralizing antibodies to be protected. We cannot avoid contagion. However, vaccination prevents the virus from having a reservoir and time to change. The virus – in its fight for survival – is moving forward with its mutation frequency (read variants, ed) and with a better ability to bind susceptible cells. If we limit the available tank – by vaccinating ourselves – we will certainly hasten the end of the pandemic. In addition to the fact that vaccination protects against the risk of serious disease evolution, ultimately from hospitalization, intensive care and death “.

You mentioned antibodies. In this regard, and in the light of the skepticism of many in particular regarding the third dose, can you explain to us if and how a person can ‘measure’ his level of antibodies, which we know will diminish after months?

“It must be said that there are no reference values ​​of the antibody titre for this type of infection, or values ​​that tell us that we have a protective vaccination efficacy. The only data are the studies conducted on vaccines that tell us that protection is guaranteed for 6-8 months, especially with mRNA ones (Pfizer and Moderna). However, immunology has always given us an important indication, namely that we do not know the vaccine efficacy based on a measured antibody titre and this precisely because immunology has always taught us that protective efficacy is based on the formation of memory cells. It therefore means that, following a new natural stimulus of the virus (thus coming into contact with us), we can regenerate an effective antibody clone. Therefore, even if our antibody titer were to be low, it is not certain that we would not respond well to a natural infection. We know that there is a test to measure the antibody titer, however, it does not tell us how many of these are effectively neutralizing “.

To simplify, we could say that quantity is not important but quality. And how does the discourse of the third dose fit into this picture you have just described?

“There are studies on the third dose that show that this is much more effective in producing a number of effectively neutralizing antibodies. They would be produced not only in greater numbers but also after fewer days. And it is these that renew our immunological memory. In medical jargon it is said that there is a greater affinity of the antibody with the viral antigen to be neutralized. The more effective the antibody is the more it binds complementary (this is the precise term) to an antigenic determinant. And this occurs at a later stage of antibody maturation. It is called ‘affinity of the antibody for the antigen’. Having said that, you shouldn’t be in a hurry to resort to the third dose, not earlier than 6-8 months after the last administration. For the single-dose Janssen, on the other hand, times are a little earlier ”.

In practice, the antibodies generated by the third dose would be the ‘best’. The virus, however, as you yourself explained many times, uses the mutation precisely to evade the antibody response. How does it come out?

“It is a struggle for survival. The virus, after a jump in species, takes some time to create a balance with its host (or us in this case, ed). Initially, in the presence of a ‘different’ host without defenses (like us in the first phase), the microbiotic agent is aggressive. But in the long run, a balance is created between the virus and the host, but for this to happen, time clearly passes. But mind you, this is already in fact happening. Of course, it must be considered that if for us a year and a half is a long time, for a virus it is not at all ”.

In this delicate phase, with the increase in infections, especially in Europe and in particular in Eastern Europe, how should we behave?

“Winter brings with it other viral infections, starting with the classic seasonal flu. Symptoms could also be confused with those of this aero-diffusive pandemic. Meanwhile, let’s go ahead with vaccinations, with respect to which Italy has already given proof of great responsibility. And then we continue with masks and spacing. They are sufficient to prevent contagion, we must not forget it “.

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