Can a dose of a different Covid vaccine than the first be done? Here’s what the science says.
Make the recall of the anti-Covid vaccine with a second dose of a different type of vaccine from the first it could be not only possible, but even more effective. The negative consequence could be a little heavier side effects, but we are still talking about minimal effects, just a few flu symptoms in the hours following the administration of the vaccine. Perhaps precisely because i feedback arriving from science they are quite encouraging, the special commissioner for the Covid emergency, the general Francesco Figliuolo, spoke openly about this possibility during the broadcast of Rai3 Elixir, of which he was a guest.
Figliolo only said: “There are advanced studies on the second heterologous dose, that is to do the first dose with Astrazeneca and the second with Pfizer or Moderna”. He then added that these studies “it seems that they give an excellent answer”. In fact, from the studies carried out in particular by the researchers of the Com-Cov of the University of Oxford in the United Kingdom and by the scientists of the Carlos III Health Institute in Spain, it emerges that by administering a first dose of AstraZeneca viral vector vaccine and then doing the booster with a dose of messenger RNA vaccine, then Pfizer or Moderna, the immune response was at least the same or even better.
Covid vaccine, second heterologous dose, is it convenient or not? –
L’immunologo Sergio Abrignani of the State University of Milan as well as a member of the technical-scientific committee for the coronavirus emergency, explained that “immunologically having a trigger (priming) of the immune response with a type of vaccine and a booster (boost) with another type, generally, based on what we know about other vaccines, in terms of immune reaction it is at least the same and often even more beneficial. Even with certain types of adenoviral vaccines it is recommended to do the booster with a different product “.
The prime-boost technique, therefore priming and booster, with two different vaccines has been widely tested in the past, it is now a question of to understand if it can be equally effective in the specific case of the Sars-CoV2 coronavirus. Scientists seem optimistic from this point of view. Also the President of the Italian Medicines Agency Giorgio Palù is of the same opinion: “Two different vaccines induce amuch more effective immunization with ten times higher antibodies compared to those that occur with the same administrations “.
Recall with a different anti-Covid vaccine: scientific studies –
But what are the scientific studies that would confirm the possibility (and usefulness) of making the second dose of the anti-Covid vaccine with a different type of vaccine than that of the first dose? So far there are mainly two studies cited in this regard, but, as Figliuolo said, it is still necessary to have some confirmations in order to allow people to actually proceed with a vaccine booster other than the first injection. The two studies in question, as we have anticipated, are a British and a Spanish one.
- It British study (researchers from the University’s Com-Cov) was conducted on 830 volunteers aged 50 and over. The research results were sent in a letter to The Lancet, an English medical science journal published weekly by the Lancet Publishing Group.
- It i study spanish (Carlos III Health Institute) was conducted on 673 volunteers (of which 221 as a control group). In Spain, among other things, the health authorities have decided to allow people under 60 who received the first dose of AstraZeneca the possibility of choosing Pfizer for the second dose, given that in the meantime the AstraZeneca vaccine has been banned for under 60.
UK study on second heterologous dose of Covid vaccine –
Matthew Snape, one of the trial coordinators of the Oxford study, told Sky News that the research results showed that mixing vaccine doses can lead to an increase in absences from work by one day after the injection, but no safety concerns emerged of patients and there are no signs of an impact on the immune response. Furthermore, this study shows that there are no big ones differences between the combination viral vector vaccine AstraZeneca as the first dose and messenger Rna vaccine as Pfizer for the second dose and the reverse, i.e. first dose with Pfizer and second dose with AstraZeneca.
Compared to using the same vaccine for the first and second doses, using two different vaccines only registered most frequently effects such as headache, fatigue, fever for a day. These are the usual flu symptoms which are the most common reaction in the first day after the vaccine, but are still described as side effects. mild or moderate. This study was started already in February in particular by verifying the interaction between the Moderna and Novavax vaccines, to understand if mixing them it is possible to have longer periods of coronavirus immunity. The effectiveness, in any case, does not appear to be lower than that obtained with two doses of the same vaccine.
Spanish study on Covid vaccine booster other than first dose –
The study conducted in Spain at the public body Istituto Sanitario Carlos III reached practically the same conclusion by inoculating AstraZeneca for the first dose and Pfizer for the second. One of the research coordinators, Jesus Antonio Frías, in a press conference explained that it is possible to conclude that “the administration of a booster dose other than the first is highly immunogenic and safe“And that the side effects are similar to those in cases where the same vaccine has always been administered for both doses and in no case were there any serious adverse reactions.
What the EMA says about the mix of doses of anti-Covid vaccine –
L’European Medicines Agency pointed out that the possible mix of different vaccines between the first and second dose, and therefore the use of a second heterologous dose, is a “very important” issue and that it is “under discussion now” because there are “some data with respect to this possibility, in particular with AstraZeneca and an mRna vaccine ”from which it emerges that“ there are no particular concerns from a safety point of view ”. The reference is precisely to the British and Spanish studies. Marco Cavaleri, head of Vaccines and Therapeutic Products for EMA’s Covid-19, added that “the few data we have seen show that even in terms of immunogenicity it seems an effective approach to generate a robust immune response after a second dose of different vaccine, ”but he also said that EMA is trying to gather“ more evidence and review studies to make sure this approach is as good as it sounds ”.
So, summing up, from the studies conducted so far and in the opinion of some illustrious immunologists and virologists such as Sergio Abrignani and Giorgio Palù, it seems highly probable that carrying out a first dose of viral vector vaccine and a second dose of mRna vaccine is not only possible and safe, but perhaps even capable of provoking a better immune response than always using the same vaccine as a prime and as a boost, that is, as a first and second dose. Even the EMA seems pretty convinced that the mix can be done without problems, however await further confirmation from the studies that are taking place on this topic.
Meanwhile, countries like France e Spain have already allowed their citizens under the age of 60 who were given the first dose of AstraZeneca vaccine to opt for a second heterologous dose, hence an mRna vaccine, given that, after cases of thrombosis, have determined that the AstraZeneca vaccine is only recommended for those over 60 years of age.
05 June 2021 (change June 05 2021 | 10:38)
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