Covid-19 vaccine: what strategy for immunocompromised people?

Becoming invulnerable to Covid-19 while having a fragile immune system is the whole puzzle of immunocompromised people. While the Prime Minister unveiled last week the roadmap for the vaccination campaign against Covid-19 which will begin in France at the beginning of January, it is interesting to look at a category of people considered to be “vulnerable ”.

A heterogeneous group of people with fragile immune systems

Immunocompromised people do not form a homogeneous group, since their pathologies are varied, ranging from someone taking corticosteroids to someone who has received a stem cell transplant. Their immune responses are therefore also specific. If at the beginning, a doubt may remain as to the effects of a vaccine in connection with the weakness of their immune system, this does not seem to be sufficient to advise against its prescription. Even without an effective immune system, vaccination against Covid-19 has more advantages for them than risks.

“I will not talk about the risk first, since the question is mainly focused around the benefitslice Benjamin Wyplosz, infectiologist in the infectious diseases department at Bicêtre hospital. The risk is that if these people get the coronavirus, they die, and there is no benefit to catching the coronavirus. On the other hand, although we do not currently have data on the risks of Covid-19 vaccines for immunocompromised people, the only risk would be the ineffectiveness of the product. To date, for the other vaccines, there is no evidence that they cause more complications for immunocompromised people.”

Some vaccines, such as chickenpox, are not recommended for immunocompromised or particularly vulnerable people, such as pregnant women, because the risk of putting their health at risk would be too great. However, as Benjamin Wyplosz points out, not all vaccines work the same way. “We must make the distinction: there are ‘live’ vaccines, and these are contraindicated in immunocompromised patients. The only vaccines that are made in immunocompromised people are not ‘live’, we speak of ‘inert’ vaccines. They are either composed of destroyed infectious agents with an inability to reproduce, or with pieces of infectious agents, which is called a subunit vaccine. These two can be done to immunocompromised people without risk in terms of vaccination, however there is a risk in terms of effectiveness if people are too immunocompromised.”

Ring vaccination to protect the most vulnerable

Regarding the two main vaccines available, namely the one developed by the American-German alliance of Pfizer and BioNTech laboratories on the one hand and that of the American pharmaceutical group Moderna on the other, they both use Messenger RNA, a temporary copy of a section of our DNA, the genetic code for all our cells. A strand of messenger RNA contains all of the assembly instructions for a cell to create a protein that protects cells in the body from infection. In the case of these two vaccines, the messenger RNA which will be injected into the body will have the mission of indicating to the cells which proteins they must synthesize to defend themselves from the coronavirus.

With this technology, there is no risk of affecting the health of people, immunocompromised or not. “Messenger RNA vaccines [de Pfizer et Moderna, NDLR] are not capable of causing disease since there are no complete infectious agents inside, supports Benjamin Wyplosz. We are on an inert vaccine, we do not take many risks because we cannot cause disease, which is why they should not be contraindicated for people with an imperfect immune system..”

However, even if some vaccines against Covid-19 currently being developed, such as Sputnik V, the one developed by Russia and the Gamaleya Institute, use transformed adenoviruses which incorporate part of the genetic material of the coronavirus, this is not sufficient. to cause health complications. On the one hand because the genetic material used is in too small a quantity to be dangerous, and also because the pieces of Covid-19 present cannot reproduce since the protein responsible for reproduction has been suppressed. “Viral vector vaccines – which consist of taking a benign virus into which the genetic heritage of the coronavirus is introduced – are not able to multiply in humans. AstraZeneca’s vaccine is a viral vector vaccine that is based on a non-replicating chimpanzee adenovirus, so there should be no problems in immunocompromised people with this vaccine..”

If, as we have seen, all the vaccines against Covid-19 currently on the market do not seem to involve any risk, this does not mean that all immunocompromised people can be vaccinated. It should always be kept in mind that each immunocompromised patient must receive protection adapted to his situation, depending on the weakness of his immune system. The last resort, in addition to herd immunity which would take too long to set up, lies in the close entourage of the patient, the only one “authorized” to transmit an infection to him. To eliminate all risks, the vaccine strategy must be based on them.

“The strategy that is systematically recommended around the immunocompromised is a ring vaccination, that is to say that all the people who are around – family, relatives, friends – are immunized and should not transmit the disease to the immunocompromised person. This is already what is done with the flu and vaccines that cannot be administered to immunocompromised people, such as measles for example. It is surely the same strategy that will be used with Covid-19, especially if vaccines prevent transmission of the coronavirus”, concludes the infectiologist.