While the effectiveness of vaccines against the virus is eulfined over the months, a reminder makes it possible to increase the amount of antibodies produced.
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What rational bases is based on CVIV-19 vaccination reminder campaign, launched on 1 September in the elderly and fragile people? First, there is a slow and progressive fall in antibody levels, over the months, in those who received two doses of vaccine. And there is also the slow climbing of infection rates. “The objective of this reminder is to amplify the reservoir of certain immune cells, the” B and T lymphocytes “. These include strengthening the pool of long-life cells that produce antibodies” Explains Professor Alain Fischer, Immunologist, Chairman of the Vaccine Strategy Orientation Board (COSV). The goal is therefore to increase the amount of antibodies produced, but also to enrich the diversity of the immune response, which could thus address more molecular targets carried by the virus.
The effectiveness of anti-Covid vaccines thus eweight over the months – it was an expected limit. One of the latest studies on the subject was published on September 6 in the journal The Lancet Regional Health-Europe . The immune responses of 122 individuals who had received two doses of the Pfizer vaccine were compared to those of 50 non-vaccinated and uninfected subjects. Six months after the second dose, the levels of antibodies against the SAR-COV-2 spike protein were similar to those measured in those who had only received their first dose.
In addition, 87% of the vaccinated individuals had developed “memory lymphocytes”, a more sustainable immune response form. However, it was, like the antibody response, weakened in older people.
Other observation in favor of a reminder: in the subjects vaccinated with two doses, the risk of infections increases over time. This shows, among others, a study conducted in 44,165 participants over 16 and 2,264 adolescents aged 12 to 15, Posted on November 4 in New England Journal of Medicine . With the Pfizer vaccine, infection protection was 96.2%, a week to two months after the second dose. Two to four months later, it was 90.1%; and after four months, at 83.7%.
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But do these declines result in real life by rising hospitalization and death rates? “This is the issue at one million dollars of the moment,” says Professor Miles Davenport, an immunologist’s model of the University of Sydney (Australia), in a journalistic article of the magazine Nature of September 17
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