A Health column to answer readers’ doubts about Covid. A way to examine news and information that sometimes turn out to be hoaxes. Here are some questions that came to the editorial office. If you have any questions, write to [email protected]
We talk about vaccines and the immune system. There is an innate (or natural) immunity, effective without a previous contact with the antigen, that component of the virus towards which our organism reacts, considering it foreign and potentially harmful. Acquired (or adaptive) immunity, on the other hand, requires initial exposure before activating defense mechanisms. In this case, following a subsequent encounter with the antigen, the response will be rapid, thanks to two ‘binaries’: cell-mediated immunity, dependent on T lymphocytes, and humoral immunity, linked to B lymphocytes, which release antibodies.
Covid vaccines: safety, duration of protection, adolescents. The answers to the most frequently asked questions
by Cinzia Lucchelli
Request
I got vaccinated last May. After a month I took a blood sample to check the response: the antibodies were negative. I asked my doctor to have the procedure again, because I believe the vaccine did not work. I was told that it is currently not expected and I may have developed cell-mediated immunity. It is true?
Reply
He answers the question Roberto Tail, full professor of Infectious Diseases at the Catholic University of the Sacred Heart in Rome.
“Yes, protection against the virus is achieved through both a humoral response, based on antibodies, and cell-mediated. Last May the FDA (Food and Drug Administration) established that the search for antibodies (or immunoglobulins) against the Spike protein is not an absolute means to exclude or validate the presence of immunity against Sars-CoV-2. This is an official position taken by an international control body, of considerable weight “.
How come some people don’t develop antibodies after the vaccine?
“It is a problem that is not easy to interpret, it could be linked to various aspects, regardless of the type of product used. There are several studies that indicate that over time the immunoglobulins tend to reduce. In some cases not finding them could be physiological, it would not compromise the protection of the organism in case of a new encounter with the virus, thanks to the immunocompetent cells. In addition, for all vaccinations, there are people whose immune system is not stimulated: they are called ‘non-responders’, we do not yet know what the precise percentage compared to anti-Covid prophylaxis. Some immunosuppressed patients benefit from an additional administration of those vaccines in two doses, reaching a protection level of around 60%. For others, however, there will be no response. They are the latest scientific evidence to testify. Finally, we must reject the equation ‘no antibodies, no protection’, because it could they are not visible: their absence, or presence, is linked to a threshold value established by the World Health Organization. But a citizen could also find himself close to that value, just below. It would be wrong to say he doesn’t have them. ”
Are there tests to evaluate cell-mediated immunity?
“Cell-mediated immunity is difficult to highlight, because it is linked to sophisticated tests, performed in specialized laboratories. In all diseases it is more complicated to study it, but the research activity has been done, it is not invented data: even if not parallel to humoral immunity, people are protected. On the contrary, antibodies are measured in a rapid, standardized way, with diagnostic kits “.
.