A series of studies allow us to be optimistic about the duration of the immunity that we can develop against the coronavirus.
The duration of immunity against the coronavirus, and in particular that conferred by vaccines, is a key issue in hoping to curb the pandemic over time. In May 2021, a set of two studies (one published in Nature, the other only in prepublication) suggested that people who were infected with the coronavirus and then vaccinated a few months later achieved particularly robust immunity that could last a minimum of a year, or even much longer.
However, this work did not give details of people who were vaccinated but who had not previously had covid. In a new study published on June 28 in Nature, the authors show that the currently used messenger RNA vaccines, Pfizer and Moderna, can also maintain robust immunity, independent of a booster shot.
Immunity that can persist
During an infection or a vaccination, “germinal centers” are formed, which are essential for the functioning of our immune system. They are, in a way, temporary factories where cells which themselves produce antibodies are generated. They are also training centers for these antibodies. In the event of infection with the coronavirus, the germinal centers develop in the lungs; in case of vaccination, they develop in the lymph nodes (in the armpits, which may explain their temporary swelling after the Moderna vaccine in some cases).
However, the authors of this study found that where the germinal centers usually decline one to two weeks after vaccination, they persist for up to 4 months after the first dose of a coronavirus mRNA vaccine (Pfizer et al. Moderna). This work shows, according to the authors, that human vaccination based on messenger RNA ” induces a persistent B-cell response of the [centre germinatif], allowing the generation of robust humoral immunity ».
What impact should these results – this study and the two previous ones – have on the duration of immunity? ” This is a good sign on the persistence of our immunity conferred by this vaccine. », Comments to the NY Times Ali Ellebedy, immunologist and co-author of this study. Because the length of time the germinal center remains active has an impact on the number and effectiveness of antibodies: the more they train, the more they can be effective against the different strains of coronavirus likely to present themselves to the body. This also reminds us that vaccines can retain some efficacy against variants, but on condition that they remain close and do not change excessively. Another logical limitation to this work is that robust immunity might not be present in the entire population (let alone immunocompromised people).
Although encouraging, further studies of this kind are needed to clarify our knowledge of the duration of immunity against the coronavirus. This only looks at Pfizer and Moderna, not other vaccines like J&J and AstraZeneca. It also does not address the Delta variant, which is currently of concern – however, other data, particularly from the United Kingdom, show that the vaccines remain very effective against the severe forms generated by this variant, which is reminiscent of the urgency vaccination.
It should also be remembered that behind the issue of individual immunity, there is also and above all that of collective immunity, in the face of the spread of strains such as the Delta variant.
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Source: Numerama by www.numerama.com.
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