The French people most at risk of severe forms of Covid are called upon to give a vaccination booster. Can this additional dose lead to an excess of antibodies, which are dangerous for the body? More side effects? Lighting with Pr Elisabeth Botelho-Nevers, Head of the Infectious Disease Department at the Saint-Etienne University Hospital.
The Covid epidemic is returning to France. The French people most at risk of severe forms of Covid are called upon to take their vaccine booster dose to avoid being infected and hospitalized, sometimes again. Can this additional dose lead to an excess of antibodies, which are dangerous for the body? More side effects? A immune system overload ? Lighting with Pr Elisabeth Botelho-Nevers, Head of the Infectious Disease Department at the Saint-Etienne University Hospital.
Are the antibodies produced after vaccination against Covid the same as after infection?
Pr Elisabeth Botelho-Nevers : When we have Covid or any infectious disease, we will become immune to the responsible microbe, that is to say, the immune system will make antibodies against this microbe that enters the body. This microbe or “virus” in terms of the coronavirus, is made up of lots of antigens (parts of the microbe against which antibodies are made). Faced with the Covid, the body makes antibodies against the S protein (Spike) which is the key to the virus entering cells but the virus is also made up of other proteins present inside. We will also manufacture antibodies directed against a part of the interior of the virus that we call “anti-N antibodies”. With certain routine serologies, anti-S and anti-N antibodies are sought. If there are only anti-S antibodies we can say that it is after the vaccination, if there is both, it is post-disease immunity. It is the anti-S which, if they are neutralizing, protect. All the Covid vaccines on the market in France are vaccines that will only induce the S protein as an antigen and therefore we only make antibodies against this protein.
If we’ve ever had the Covid, we have antibodies. What then is the point of the recall?
Pr Elisabeth Botelho-Nevers : Not everyone is immunized the same way after illness. Between people who have had a very mild Covid or even without symptoms and those who have had serious forms, the quality of immunity is not the same. In addition, if we did the covid a long time ago, our natural immunity may have diminished or, if we became infected with the initial virus, we may have a response to the less effective delta variant. Vaccination will stimulate the immune system in a different way and broaden the range of the immune response. The best immune response is to have had the disease and then to have been vaccinated. On the other hand, by having had the disease, we were able to have a serious form, a long covid etc … therefore do not seek to immunize naturally !
Can we have too many antibodies after the 3rd dose?
Pr Elisabeth Botelho-Nevers : No. The vaccine booster is a boost. If you have antibodies, that’s fine, it will comfort them and make them rise, which is not a problem in itself. There will be no antibody “explosion”.
“There is no danger in giving a booster dose. Boosting his immunity is not a problem. “
Is there no risk of immune overload with a 3rd dose?
Pr Elisabeth Botelho-Nevers : No, there is no danger in giving a booster dose. Boosting your immunity is not a problem. Either you still have antibodies and you will be all the better protected against reinfection. Either your level is a little low or your antibodies are not effective and this boost will protect you. Il is aimed at people who have risk factors for severe forms of Covid, these are particularly vulnerable populations. We must not forget that when you get vaccinated, you encounter a lot less antigens than when you encounter the infectious agent and have the disease. The human body is constantly stimulated because we encounter antigens on a daily basis, our immune system faces them. When we come to vaccinate someone, against Covid or other, the amount of antigens is minimal compared to that to which we are exposed every day.
“It is a little illusory to look at your serology to say to yourself” I do or I do not do my dose “.
Is it relevant to do a serological test before your 3rd dose to know your antibody level?
Pr Elisabeth Botelho-Nevers : Analyzes are underway to find correlates of protection. There is no clear and certain threshold to be sure that you are well protected. For the moment it is therefore a little illusory to look at his serology to say to himself “I do or I do not do my dose”, especially as the virus is circulating again and the people concerned by the boost have factors of serious risk. The idea is to prevent these people from being hospitalized because of a covid. If serology can be done easily, not all use the same techniques and the value may vary from one laboratory to another. The analysis will look at the antibodies but not necessarily correlate with the neutralizing antibodies that protect against the disease. These are not routinely sought after. It is therefore possible to have a level of antibody X without being protected.
Do we know the level of antibodies from which we are protected against the virus?
Pr Elisabeth Botelho-Nevers : No, but work is in progress. In any case, a high antibody level does not necessarily mean that you are completely protected. There are people who have lower levels but who will have cellular immunity that will protect them more against the disease.
Can the side effects after the 3rd dose be stronger because the immune system is stressed again?
Pr Elisabeth Botelho-Nevers : In practice, there may be a little more reactions but this is not related to the prior existence of antibodies. We do not all react to the vaccine. It depends on the age. On the 2nd dose, subjects over 50 years of age had less reactogenicity than young subjects with RNA vaccines. As the boost mainly concerns older people, there will not necessarily be many more side effects. And we stay on mostly mild reactions like a injection site pain or one mild flu syndrome regulated with a little paracetamol. The benefit of vaccination over the risk of side effects is always present. The notion of boost is concomitant with a decrease in immunity and a re-increase in the number of Covid cases so this dose is important. But we must not forget that being vaccinated is already very important. We still currently have hospitalized Covid patients who are not vaccinated at all, including those over 80 years old. Vaccination, if it does not completely protect against infections, protects against serious forms requiring hospitalizations. The Covid vaccines we have are drugs that have been administered to millions, even billions of people, for which there is a great deal of extremely reassuring data in terms of safety and efficacy.
Thanks to Prof. Elisabeth Botelho-Nevers, Head of the Infectious Disease Department at the Saint-Etienne CHU. Interview on November 15, 2021.
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