What do post-vaccination antibody tests mean in relation to COVID-19 immunity?
Cyprus International University (CIU) Faculty of Pharmacy Vice Dean and Molecular Microbiologist Assist. Prof. Dr. Ender Volkan Çınar, stated that there are two types of immunity against SARS-CoV-2, and went on to advise that they are, “humoral immunity, which obtains antibodies developed against the virus, and cellular immunity, which includes T cells and other cells that fight the virus. In order to have full immunity against SARS-CoV-2, you need to have both” she confirmed.
Giving information in relation to humoral (antibody) immunity, Assist. Prof. Dr. Çınar stated, "out of the antibodies our bodies created to fight SARS-CoV-2, the most important antibodies are the ones that can inactivate the virus with a ‘neutralization’ capacity”.
Stating that the antibodies that have the closest relationship to these values are those that bind to the Spike (S) protein 'receptor binding' region and sometimes the 'N-terminal' region of the virus, Çınar elaborated, “Even if it is not clear how much these are able to inactivate the virus, compared to the antibodies that are developed against other parts of the virus, it is more informative than the effectiveness of the bodies response to the vaccine”.
It cannot be concluded that a person is protected against SARS-CoV-2 with an increased antibody level
Explaining that the minimum antibody values required for immunity against SARS-CoV-2 are not yet known, Assist. Prof. Dr. Çınar stated that following vaccination, there is no antibody level where it can be said that the individual has protection against SARS-CoV-2, only that it can display whether the immune system has reacted to the vaccine or not”.
Pointing out that at the society level, antibody measurements following vaccinations are scientifically important, Çınar underlined that individual-based antibody tests provide a general idea about the body's response to the vaccine, however they do not give information in relation to whether the individual has gained protective immunity against the virus or in the event they are infected with the virus, whether they would be able to transmit the virus to someone else.
Advising that it is preferred for there to be a certain increase in antibodies following the first dose in double-dose vaccines, Çınar stated that it is expected for antibody levels to increase even more so after the second dose.
Pointing out that even if after an antibody test is performed and an increase in the level of antibodies is observed, it is still necessary to continue to be protected by observing the mask - distance - hygiene rules, and that the increase in antibody levels does not provide 100% protection, Çınar emphasized that in order to achieve full protection, other branches of the immune system, such as cellular immunity, should be activated.