Reacción a "Expert reaction on EMA recommendations on extra doses and boosters"

I think there are two different issues here: (1) third dosein transplant patients (the mentioned studies do not refer to other types of immunosuppressed patients), and (2) booster dose in healthy people who have already received two doses.

(1) In my opinion, it is important to conduct these studies in immunocompromised patients, since they are the most vulnerable to SARS-CoV-2 infection. Their immune systems do not function or function incompletely and,therefore, their response to vaccines may be much lower than desired/expected.Therefore, a priori, and provided the administration of the third dose is safe,I believe it would be appropriate to administer a third dose.  

In this regard, the study by Kamar et al is retrospective, in transplant patients immunized with Pfizer, in whom they observed thatantibody titers increased after the third dose. In my opinion, this ispromising, although they have not tested whether or not these antibodies areneutralizing and/or can fight infection. It is basically descriptive of a fact (increase in antibody titers), it would remain to be demonstrated that, indeed,their immune systems are, after the third dose, better able to fight the virus.

Regarding the study by Hall et al, I see it as much morecomplete since it is a clinical trial (NCT04885907). In this case they do lookat whether the antibodies are neutralizing, and they do a small analysis of thephenotype of T lymphocytes specific for SARS-CoV-2. So administering the third dose of Moderna in transplant patients seems safe. However, they themselves indicate that their results do not (yet) indicate that this third dose endows them with resistance to infection, since a longer follow-up period is necessary.

Therefore, I believe that these studies suggest that thethird dose could (conditional time) be effective in transplanted patients.Given the current medical urgency, I understand that the EMA approves its use,even if they have only "circumstantial" evidence of efficacy, sincein light of these studies it appears that the administration of the third doseis safe in transplant patients, but they are not conclusive that it iseffective.

The press release generalizes the use to allimmunocompromised patients - I have not done a literature search for third doseadministration in immunocompromised patients (e.g. from cancer treatments, orwith autoimmune diseases). I believe that the EMA wants to open the third doseto all immunosuppressed, although the two studies you mention are only intransplant recipients.

In conclusion, I understand that the EMA, based on thesestudies, extrapolates to all immunosuppressed patients that the administrationof the third dose is safe and could be effective. Surely before the pandemicthey would wait for more data to issue this opinion, but given the currentcircumstances they prefer to go ahead, seeing that it seems to be safe. It maynot be effective afterwards, but just in case.... In fact, they make it veryclear in this sentence: "Although there is no direct evidence that theability to produce antibodies in these patients protected against COVID-19, itis expected that the extra dose would increase protection at least in somepatients. EMA will continue monitoring any data that emerges on its effectiveness".

(2) Regarding this issue I give you my personal opinion: in my opinion, a third booster dose in a healthy, "young" and non-immunosuppressed population would be something interesting to consider, but perhaps not now. I believe that the objective should be that other less favoredcountries, with fewer resources, have access to these doses in order to be able to vaccinate their population with the corresponding doses, and from there to evaluate that the countries with more resources receive a third booster dose.If the virus continues to circulate freely throughout entire countries, it will continue to mutate and generate resistant strains.