Manel Juan
Head of the Immunology Service
In the immunosuppressed population, such as solid organ and hematopoietic transplant recipients, there is a small part that with two doses is not immunized, hence the recommendation for a third dose.
These are not all immunosuppressed persons; many will be protected after two doses of the vaccine, but even so, the third dose is chosen for simplicity, because it is complicated to identify those who, although they do not have antibodies, have developed cellular immunity. It is well thought out because these patients are already exposed to many infections and SARS-CoV2 infection can give a very serious COVID19.
In any case, what the EMA says is what it can say, which is that a third dose 'can' be given. It it harmful? No. Is it necessary? Well, when half the world is still unvaccinated, and precisely because of this we are risking the appearance of a variant for which the vaccines do not work... Well, no, it does not seem necessary... Nor does it seem the best thing to do in the general population.
It is normal that the EMA has aligned itself with this tolerant position towards allowing additional doses, ... even more so when the interests are many. The companies that have produced the vaccines have made and continue to make a lot of profits, and they continue and will continue to lobby. It is easy to get the idea that if something is good, such as a vaccine, the more the better, but in this case it is not so: you cannot be 'highly immunized' in the same way that you cannot be 'highly pregnant'.
Immunization as a concept of "being protected" from suffering a particularly serious disease after contact with the virus, means having it or not having it. Having more antibodies does not mean being more protected, ... the important thing is to have specific cellular immunological memory.
In any case, the EMA does not say that a third dose must be given, but that it can be done.
"On the other hand, a third dose to severely immunocompromised individuals does not jeopardize the availability of vaccines for those who are not reached, as in the third world, because they are a small volume of individuals. But if the decision is made to give it to everyone, it does."
We have vaccines that with two doses after one year continue to provide protection to practically the entire population. We do not have data beyond one year because we cannot have them, but for now the protection is there.