How long does the disease-induced protection last and how long is vaccination protection? Do vaccines work against the variants that have emerged so far? Why is it better to get vaccinated even if you have already contracted the virus? There are many studies that attempt to answer these questions. But if in some cases the crystal ball is needed – as for the duration of immunity -, for others the answers are beginning to become clear. A recent study published in Lancet Microbe estimated – based on the behavior of coronaviruses – that natural immunity due to the encounter with the virus could last a maximum of two years. But if we consider that the protection generated by the disease plus a dose of vaccine is extremely higher than that generated by the disease alone, the choice to vaccinate even the ex-patients is more correct than ever. In this regard, a study just published in the journal Nature by the TLS Foundation Monoclonal Antibody Discovery (MAD) Lab led by Rino Rappuoli, has identified in the blood of individuals with a previous infection and vaccinated which are the memory B cells best able to neutralize the variants present today. A fundamental indication both in support of the need for a third dose and a clear indication for the design of the next generation of anti Covid-19 vaccines.
Tumors and Covid vaccine, Cognetti: “Immunity lasts nine months: the third dose is needed”
How does the immune response work?
When our body comes into contact with a harmful external agent such as Sars-Cov-2, it produces an immune reaction consisting of two phases: the non-specific one – already present at birth and not dependent on previous encounters – and the specific one, directed precisely against that particular external agent. The latter is essentially mediated by two types of cells: B lymphocytes and T lymphocytes. The former are responsible for the production of antibodies, the latter for the cellular response to the virus. In both cases, following an infection or vaccination, specific memory cells are created that are able to be activated in the event of an encounter with the pathogen.
The duration of protection
However, how long the protection lasts depends on many variables. If for some pathogens immunity can last for a lifetime – think of vaccinations carried out by children – for others it needs a booster. As for Sars-Cov-2 this still remains a mystery, since the virus has been present among us for less than two years. According to an analysis carried out by researchers at the Yale School of Public Health, immunity would not last that long. To reach this conclusion, the researchers crossed the data relating to Sars-Cov-2 reinfections with those relating to the behavior of other similar coronaviruses such as Sars-Cov and Mers-Cov. In this way, a predictive model has been developed according to which immunity obtained naturally, or through the encounter with the virus, will not exceed two years.
Covid, because our immune system responds differently to infection and vaccine
by Jacopo Vergari
Disease and vaccine, maximum protection
But beyond this prediction, which will find confirmation only in the observation of reality, the studies published to date on immunity clearly indicate that “making the disease” – beyond the danger and the aftermath of long-Covid induces an immune response comparable in efficiency to a complete vaccination course or to a previous infection plus a dose of vaccine. But let’s go to the data: a study carried out by the US CDC showed that in the elderly in nursing homes the chances of reinfection in the unvaccinated (but with a previous infection) are 2.5 times greater than in the vaccinated. Not only that, a study published on Nature showed that with a single dose of vaccine post-exposure to the virus the immune response is far greater than the already important one caused by the two vaccine injections. A quantifiable response, in terms of antibody production, between 25 and 100 times higher and also effective against variants never encountered previously, a sign that antibodies evolve over time and improve.
Covid vaccine, why haven’t I developed antibodies?
by Jacopo Vergari
Vaccines in varying sizes
Therefore, it was established that full-cycle vaccination and single-dose post-infection vaccination produce a “better” response than the disease alone, the study just published in Nature the TLS Foundation’s Monoclonal Antibody Discovery (MAD) Lab has gone further by adding a fundamental piece of knowledge. “Previous studies – he explains Emanuele Andreano of the MAD and head of the Covid19 Project – have always investigated the “polyclonal” response of vaccination to the different variants that have emerged over time. In other words, they have always evaluated the ability of the antibodies present in the blood to neutralize the different viral forms. In our study, on the other hand, we wanted to characterize, by analyzing each single B cell capable of producing antibodies, which were the best in terms of neutralization of the different viral variants “.
To do this, the Italian scientists compared the serum of individuals immunized by vaccination and individuals with a previous infection plus a dose of the vaccine. “From the analyzes – continues the expert – we were able to isolate those B cells that best respond to the variants in circulation today. Having done so is of fundamental importance for the future of anti Covid-19 vaccinations. Knowing which antibodies produced that best neutralize the virus we have the necessary information – it is the concept of antigen-design – to “adapt” the vaccine and thus have a production of antibodies capable of recognizing the virus that is no longer the original one isolated in Wuhan “.
Yes to the third dose
But the MAD study provides a further indication about the possibility of a third dose of the vaccine regardless of the person’s health status (remember that to date, in healthy individuals and under 60 years of age, vaccine protection against serious disease remains very high. , close to 93%). “As demonstrated by various analyzes, over time the antibodies mature and become more and more specific against the pathogen. In our study we have shown that there is a difference between vaccine immunity alone and” hybrid “immunity, ie that induced by disease plus vaccination. A difference in favor of the latter. This characteristic supports the third dose hypothesis for all vaccinated individuals in such a way as to obtain a “maturation” of the antibodies useful to respond to the variants that emerged “concludes Andreano.
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