SARS-CoV-2 mRNA vaccines are very effective in preventing COVID-19 and especially severe disease. However, the emergence of new strains of concern, as characterized by the World Health Organization, strains of SARS-CoV-2 with high transmission potential, raises concerns about the duration and degree of protection after vaccination. The Doctors of the Therapeutic Clinic of the Medical School of the National and Kapodistrian University of Athens Theodora Psaltopoulou, Giannis Danasis, Panos Malandrakis and Thanos Dimopoulos (Rector of EKPA) summarize the findings of a recent publication by Goel et al. in the prestigious scientific journal Science (Goel et al., Science 374, 1214 (2021)). The researchers wanted to study immune memory after being vaccinated with mRNA vaccines against SARS-CoV-2 and specifically identified both the presence of antibodies to the virus antigens and the memory of B- and T-lymphocytes in 61 people who were vaccinated up to 6 months after vaccination. 16 of the 61 people had previously had COVID-19.
Vaccination resulted in high immune responses, and antibodies against S-protein (anti-spike), receptor binding site (anti-RBD) and neutralizing antibodies remained high at 6 months after vaccination, although that the antibody titer decreased over time. It is worth noting that the inoculation resulted in the production of memory B-lymphocytes against the receptor binding site (anti-RBD) that showed cross-reactivity with the receptor binding sites of strains Alpha, Beta and Delta. It is also interesting to note that these memory B-cells continued to grow between 3 and 6 months after vaccination. Compared with natural COVID-19 disease, mRNA vaccination resulted in higher memory B-lymphocyte titers by cross-reactivity with anxiety strains at 6 months.
In addition, the researchers found that high levels of CD4 + T cells after the first dose of the vaccine were associated with high levels of antibodies at 6 months after vaccination, highlighting the importance of T-cell immunity for B-humoral immunity and production. and maintenance of antibodies. In addition, vaccination in individuals previously diagnosed with COVID-19 resulted in a marked increase in circulating antibody titer due to the presence of memory B-lymphocytes. However, no long-term increase in memory B- and T-lymphocytes was observed after vaccination compared with those who had not previously been diagnosed with COVID-19.
In addition, there was no difference in the rate of antibody decline after vaccination in those with a previous history of COVID-19 compared with those who had not previously been diagnosed with COVID-19. According to the authors, this probably means that the benefit of booster doses may be a strong but transient increase in the titer of circulating antibodies against SARS-CoV-2.
In conclusion, this study highlights the role of memory B- and T-lymphocytes which are a persistent form of immune memory against SARS-CoV-2 after vaccination, even when the antibody titer is low. This parameter may be responsible for protection against severe COVID-19 disease even at low antibody titers to SARS-CoV-2 despite the emergence of new strains of concern.
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