The percentage of effectiveness of the Covid vaccine indicates that we do not all respond in the same way. The serological test tells us if the vaccine worked on us.
We have all become test experts: molecular, antigenic, serological. The first two – the classic and the rapid swab – are those that indicate whether we are positive and whose results are those published every day and on which we rely to understand how the pandemic is going. The serological test instead tells us if we have met the virus and therefore if we have been infected, even without knowing it because asymptomatic.
In fact, the test shows whether we have developed the antibodies that our body produces when it encounters the virus: IgM and IgG. immunoglobulins M indicate recent contact, while immunoglobulins G indicate an infection that occurred even months earlier. Serological tests also measure the amount of antibodies produced, which differs from person to person, and which allows immunity whose duration is not yet clear: we are talking about 5-8 months but also more than a year.
How to find out if the vaccine worked
With the arrival of vaccines, the serological test has a new important function: to find out if the vaccinated person has developed antibodies and in what quantity. In other words, find out if and how well the vaccine worked. When we hear that a vaccine has an efficacy of, for example, 80%, it means that, out of ten vaccinated people, two are non-responders, that is, they do not develop antibodies or develop few of them. In short, all vaccines are effective, what changes is the amount of people who may not respond.
Vaccination is a stimulus to the production of antibodies and seems to produce more of them than the virus itself produces on average, but in the elderly – whose immune response is lower than that of young people – and in other categories at risk, to know if one is among which ones the vaccine worked on and how many antibodies were produced matters.
Screenings with serological tests
On these issues we questioned Professor Silvia Angeletti who teaches Clinical Pathology and directs the Campus Bio-Medico University Hospital in Rome. Watch the video of the full interview.
"In all types of vaccines, even those for the flu, there may be non-responders. (…) In this phase in which a new type of vaccine is being used, we think of the RNA vaccine, and little is known about this virus, it would be useful to subject the vaccinated, 10-15 days after the second dose, to a screening serological to see if they actually responded. "
Although mass screening in this sense is not currently envisaged, serological tests will be carried out in health facilities and in those in which there is contact with risk categories, as well as in limited geographical areas for study purposes.
For example, the president of the National Research Council (CNR), Massimo Inguscio, has announced that a large serological investigation is about to start to study the response to anti-Covid vaccination. 10,000 volunteers selected from all Regions will undergo serological tests. The investigation, carried out within the Virus Memory project, should also provide useful knowledge and tools to give faster responses to the next pandemics.
Should anyone who has had Covid get vaccinated?
Serological tests during vaccination have other important functions. The data collected are in fact very important for studying the virus, its variants, the vaccines themselves, as well as vaccination priorities and therefore the best way to "herd immunity". For example, knowing who has already contracted Covid, and therefore has protection against the virus, serves to understand who and when to vaccinate.
Giuseppe Ippolito, scientific director of the Spallanzani Institute and infectious disease specialist of the Scientific Technical Committee, said: "Those who have already had Covid should not be vaccinated because they have natural antibodies. If anything, the level of antibodies will have to be checked and when these fall, a vaccination can be considered ”.
As Professor Massimo Galli, director of the infectious diseases department of the Sacco hospital in Milan explains: "The probability of having reinfections is very low. If we take a Qatari job, out of more than 100,000 people healed this is 0.2 per 1,000. (…) I am firmly convinced that we must realize that we cannot use the vaccine even when it is not needed, since it is not so much. And the only context in which I believe it is not needed, at least immediately, is that of people with a previous infection. "
Looking for the answers
It is good to remember that the scientific community is using all available means, including tests, to learn more about the virus and its variants, and to understand how to treat those who have already contracted the virus. There are also ongoing comparisons to evaluate the timing of booster doses. In Great Britain and France they are extending vaccinations to a large number of people using the available doses as best they can, as IgG antibodies reach a very high titre after the first dose of vaccine. Unfortunately – but this is always the case – the scientific community needs time and confirmed evidence to better study the virus, fight it and render it harmless.
For all of us who are not scientists, what will win this unwanted battle is correct information, attention and patience.
With the non-conditioning contribution of Abbott.
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