Not just vaccination, Covid-19 infection could also provide good protection. A pilot study, conducted by the Sheba Medical Center hospital, in Israel, shows that in people cured of coronavirus, who had not been previously vaccinated, the antibodies produced by the immune system are gradually more efficient, with better performance over time and still present. six months later.
This progressive growth, on the other hand, would not manifest itself in vaccinated and non-infected people, who still have valid coverage. The result, which for now concerns a small sample of participants, in no way suggests that vaccination is less effective, but confirms the protection provided by being exposed to Covid-19.
Research also shows that in some cases this could last even longer than expected. The data will be presented at the European Congress of Clinical Microbiology & Infectious Diseases, in Lisbon from 23 to 26 April 2022.
Vaccinated and cured, what happens at six months
The study stems from the desire to understand whether a previous infection can provide a more lasting defense than vaccination. The question arises from the fact that in Israel in 2021 many health workers vaccinated for six months became infected, while people who were not vaccinated and cured were not infected.
The researchers, coordinated by Carmit Cohen of Sheba Medical Center, followed 130 patients who tested positive for coronavirus, from March to November 2020, before the delta variant arrived in Israel. In particular, in today’s study they looked at the data of 130 people affected by Covid-19 and not vaccinated. They then compared this information with that of 22 never infected individuals, who instead received two doses of the vaccine.
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We know that both vaccination and infection stimulate the immune system to give rise to a protective response, both through the production of specific antibodies and immune T cells. to antibodies, and focused on a specific parameter, the so-called “greed index”. This index, which is a number, somehow measures the performance of antibodies, that is, their ability to bind to the virus, neutralizing it.
In other words, the team evaluated how efficient the antibodies are in their task and this test took place at 2 different times: one month after vaccination or the onset of symptoms and then six months later.
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The results
After one month, the level of antibodies and their “performance” are greater in vaccinated people than in infected people. But once six months have passed, the situation seems to have changed a bit.
In all groups the amount of antibodies decreases, although generally more rapidly in vaccinated people. Given this decrease, after six months the performance of the antibodies of the recovered were even increased, while in the vaccinated they remained stable.
This element, the authors point out, suggests that a previous infection could protect these people from re-infection, perhaps even more than those who were simply vaccinated.
It’s not all. In participants with a body mass index (BMI) greater than 30, therefore in the presence of obesity, the level of antibodies is higher, in the various moments of the test, than that of those with a Bmi below 30. And this, according to of the authors, it is an element of surprise.
How to interpret the data
“Although very initial, given that it is carried out on a small sample of participants, the research is interesting,” he comments Massimo Andreoni, Scientific Director of the Italian Society of Infectious and Tropical Diseases (Simit) and Full Professor of Infectious Diseases at the University of Rome Tor Vergata. “On the one hand, in fact, it confirms the presence of the good protection provided by natural Sars-Cov-2 infection, on the other it shows that this could last up to six months”.
In general, continues the expert, we already know that vaccination generates a more concentrated and strong immune response in the period immediately following the injection, with coverage that then diminishes. While the immunity associated with healing is less immediate and more diluted, i.e. it grows and develops over a longer time.
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The authors now aim to study even better the reaction of the immune system in those who have had the delta and omicron variant. “The coverage provided by the vaccination is targeted on the coronavirus spike protein, while that due to a previous infection is less specific. We could say that it is ‘multi-district’, since more parts of the virus are affected,” adds Andreoni.
“In view of the results of the study and also on the basis of this data, it will be interesting to understand if and how much re-infection with different variants of Sars-Cov-2 are frequent in this case”. The aspect linked to the BMI will then have to be clarified. “The data are very limited and to be explored”, concludes the expert, “recalling that obesity is an important risk factor for the development of severe forms of Covid-19”.