Scientists from Italy and Sweden have determined the duration of natural immunity in COVID-19 patients.
As it turned out, in most of those who had had coronavirus, the number of antibodies significantly decreased during the first half of the year, and then was fixed at the same level for 15 months. RIA Novosti writes with reference to the bioRxiv.org preprint database, which published the results of a study that scientists collected 188 blood tests from 136 patients in whom the disease was both mild and severe. The control sample included plasma of 108 participants with a negative PCR test.
The source notes that during the research, experts measured the titers of anti-S and anti-RBD antibodies in blood plasma. Antibodies of the first group target the entire S-protein of the virus, the second – at the receptor-binding domain (RBD) of the viral protein, which determines the binding of the virus to the cell. The main goal of the study was to determine how long antibodies remain active in plasma cells.
As a result of the research, scientists noted that at the peak of the immune response, those participants who had been ill had levels of anti-RBD immunoglobulins IgM and IgA of 77% and 85%, but within six months or 15 months their number decreased to 4.5% and 11% respectively. At the same time, IgM and IgA antibodies to the S-protein increased to 88% and 90% within one to three months and decreased by 50% after 55-56 days.
The titers of specific IgG antibodies to RBD and S-protein in the vast majority of patients, it is noted that this is 94% of the total number of participants, reached a maximum 15-28 days after the onset of the first symptoms, and then decreased fourfold by the end of the first half of the year and remained at the same level for 15 months.
At the same time, the titers of the same antibodies in participants vaccinated with the first dose of drugs against coronavirus were the same as in those who had recovered six months after infection. And those who received the second dose of the vaccine had antibody levels that matched the maximum natural response of those who fully recovered.
As a result, experts came to the conclusion that antibodies to coronavirus are present in blood plasma up to 15 months after infection.
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