Doctors explained why, after being vaccinated against coronavirus, some patients who are tested for antibodies to SARS-CoV-2 sometimes get negative results. The chief physician of Invitro-Siberia, Andrei Pozdnyakov, indicated that they were undergoing an incorrectly selected laboratory test.
The doctor said: “The post-vaccination test is antibodies to the IgG spike (S) antigen. Why is it also called post-vaccination? Because all available and most vaccines under development use the SARS-CoV-2 spike antigen as the target antigen administered to the body. It is against him that antibodies begin to be produced. “
In the structure of the virus itself, several antigens (antibody producers) are identified. So, for example, nucleocapsid and spike give the strongest response from the human immune system. Two different types of laboratory tests are used to determine the presence of IgG antibodies.
Previously, the most popular medical tests among Russians were named. The leader in frequency in the fall-winter of 2020 was the analysis for ferritin, a protein that shows the reserves of iron in the body. Ferritin also works as a protective protein in the body’s immune reactions when pathogenic bacteria, viruses, etc. enter it. A ferritin test is taken to diagnose anemia, lack or excess of iron in the body. According to clinical guidelines for the treatment of iron deficiency anemia, ferritin levels below 30 μg / L are already indicative of latent iron deficiency.