How long is the protection conferred by Covid vaccines? In recent months there have been several studies that have analyzed data on the vaccinated population. The latest research is Italian and collects data from 2,179 operators of the Niguarda Hospital in Milan, who participated in the Renaissance clinical study, research that intends to evaluate the immune response to the vaccine in the long term (from 14 days to 1 year). Six months after the completion of the vaccination course, antibodies continue to be present in the bodies of the vaccinated. Despite the physiological decline in the number of antibodies themselves, only 0.4% of the vaccinated have contracted the virus, e of these 9 out of 10 asymptomatically. This is the first study launched in Italy and one of the largest in Europe in terms of case studies, explains a note from Niguarda.
All study participants completed the vaccination course between January and February 2021, with Pfizer / BioNTech Comirnaty vaccine. “With the first two analyzes, ie 14 days and 3 months after vaccination, we had observed an antibody response in about 99% of the vaccinated”, he commented Francesco Scaglione, director of the chemical analysis and microbiology laboratory of Niguarda. The serological studies after 6 months confirm that in the same percentage of vaccinated people, ie 99%, there is a good presence of antibodies in the circulation. Among the few (1%) who do not show a detectable response, some from the beginning, there are also subjects with a clinical condition of immunosuppression.
In the 6 months, the average antibody titre naturally dropped, the research continues. In particular, the reduction curve was sharper and faster in the first 3 months (between 14 days and 3 months the decline was about 70%) and slower and more gradual in the subsequent period (about 45%). However, 86% of the sample studied has, 6 months after vaccination, a titer below 1,000 Bau (Binding Antibody Unit), 6% a titer between 1,000 and 1,500 Bau, 3% between 1,500 and 2,000 Bau and 4% a security higher than 2,000 Bau. On the other hand, 1% did not have a detectable antibody response.
“It is important to underline that 4% of our population still has very high qualifications, higher than 2000 Bau – Scaglione points out – 51% of these had a history of Covid-19 prior to vaccination, while 45% have never come into contact with the virus “. There is another fact to keep in mind and it concerns the number of people who became infected after vaccination, the study continues. “The data on infections are extremely comforting – continues the researcher – only 10 health workers, in fact, have contracted the infection and, above all, 9 out of 10 asymptomatically or paucisymptomatically and only one symptomatically. Among other things, in this case it was one of the frail subjects who had not initially responded to the vaccination“. Even in the presence of a relatively low number of antibodies evidently, once in contact with the virus, it seems that an effective and rapid response is activated thanks to the T lymphocytes, the ‘sentinel’ cells that allow to produce lasting protection against Covid thanks to the so-called ‘immune memory’. “The results of the study stimulate us to further investigate the dynamics of the immune response and confirm that the best weapon against the spread of the virus is the widest possible vaccination” concludes Scaglione.