How to know if a person is protected against COVID-19

26.6% of the world’s population has already had access to at least one dose of the COVID-19 vaccine. 13.2% have already received the two doses that complement the device to reduce the risk of catching the coronavirus, developing complications and dying. With these advancements, some changes are being made to mobility and compliance with restrictions that exist in different cities to also reduce the circulation of the virus. After a person is infected or after receiving the vaccines, antibodies are generated that serve as a defense against possible exposure to the coronavirus. Thanks to a test, it is possible to know if each person already has antibodies.

Antibodies are proteins that are part of the immune response against infection. They are produced by B lymphocytes and are generated, or reactivated, during infection. It is important that they have a neutralizing capacity to fight pathogens: they bind to the virus and block its ability to infect cells.

Scientific studies indicate that neutralizing antibodies appear one or two weeks after the onset of coronavirus infection. During this time, her peak activity would occur at four or six weeks.

The presence or absence of neutralizing antibodies against the coronavirus can be detected using various tests. One type of test is serological for antibodies. The reactivity of antibodies against structural proteins of the virus is correlated.

It is not yet clear how long the immunity lasts. There have been all kinds of delays and, in some studies, possible permanent immunity has even been mentioned. For the moment, evidence suggests that the antibodies will persist for at least six months, and that the decrease in their number varies from person to person depending on factors such as age and the severity of the previous infection with COVID-19.

The serological test is an antibody test that gives information depending on the antibody being measured. Elevated IgM levels speak of an acute infection, current or recent. On the other hand, high IgG levels tell us of a past infection. Because the tests can measure quantitatively, the number of these antibodies helps provide information about each person’s immune response.

In addition to letting us know if a person has overcome COVID-19, the serological test is useful for understanding and tracking the immune response to vaccination. They appear to be an important strategy for ensuring that, by monitoring over time, data are available that allow the efficacy of vaccines to be assessed in the medium and long term, and that are used to make decisions such as confirming the response after the vaccination, decide on the number of doses or define memories.

The ability to detect and quantify antibodies associated with virus neutralization may become more important as vaccine use becomes more widespread. This could be even more important if people have certain conditions, such as cancer patients, immunocompromised, transplant patients, or people with diabetes. In their case, it is a question of ensuring protection and of assessing, in the light of their results, whether a booster vaccination might be necessary.

Antibody tests can be performed in a private specialized clinical laboratory, generating reliable results and providing quantitative and qualitative data. They involve a blood sample, which will be analyzed and a result is obtained within a short period of time.

Also collaborative projects between scientists and public hospitals, such as the COVID-T platform, which is used to monitor the response of antigen-specific T cells in recovered COVID-19 patients and vaccinated individuals. It was developed by scientists from the Institute of Biology and Experimental Medicine (IBYME, CONICET), led by Conicet’s principal investigator, Gabriel Rabinovich, and led by CONICET academics, Florencia Veigas and Montana Manselle Cocco.

They had the collaboration with the Biobank of Infectious Diseases (BBEI) of the Institute of Biomedical Research on Retroviruses and AIDS (INBIRS, CONICET) and the General Hospital of Agudos “Dr. Ignace Pirovano”. Through the “COVID-T” platform, a comparative study of the extent and nature of memory T lymphocytes generated in volunteers immunized with different vaccine regimens and in patients recovering from the disease over one year will be carried out. It will provide useful information for short, medium and long term decision making, and for the design of new immunoprophylactic and immunotherapeutic strategies in the pandemic scenario.

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