Health Minister Roberto Speranza announced at Che Tempo that it is possible to proceed with a third dose of the vaccine. A third dose of the vaccine will most likely be required, a booster that will likely be “modified” to cover the variants. It will therefore be necessary to pass from an extraordinary phase to an ordinary phase and I think that this new ordinariet can be entrusted to our extraordinary network of general practitioners.
The recall with mRNA
But what do we know ofa third dose of the coronavirus vaccine? So far only the government of Boris Johnson has announced the third variant-based recall for its citizens, which will take place, he says, starting in September. Trials are underway around the world to evaluate the effectiveness of vaccine mix to proceed with any recalls. In Germany they are already doing this. in fact, it is likely that the third dose will be administered with an mRNA product since the adenovirus-based vaccines (AstraZeneca and Johnson & Johnson) are less effective with boosters due to the immune response against adenoviruses induced with the first injection. A Spanish study of 600 volunteers concluded that the vaccine mix (first dose AstraZeneca, second Pfizer) is highly effective and is not problematic. Notably the second dose increased by seven times the presence of neutralizing antibodies. From an immunological point of view, “prime and boost with different types of vaccines is feasible and probably the best choice,” says Sergio Abrignani, immunologist at the University of Milan.
Experiments with the third dose
In the United States they are already testing the third booster dose with Moderna’s mRNA vaccine. The company has created an ad hoc product, with a lower dosage, against the South African variant and which, according to the company’s announcements, also works against the Indian variant. The company is also looking to develop a single vaccine for coronavirus and flu and expects it to be ready in 1-2 years.
The UK has instead initiated a specific trial to study which vaccines to use as booster doses both to protect against new variants, and to prevent hospitals from being overwhelmed by potential new waves of infections. The Cov-Boost study aims to investigate theimpact of a third dose on patients’ immune responses by studying the effect of an additional dose on 2,886 participants, in addition to the two doses of Pfize-BioNTech or Oxford-AstraZeneca vaccines they have already received (these two products have so far been used in the UK). All participants will be monitored during the study for any side effects and blood will be drawn to measure immune responses on days 28, 84, 308 and 365. The additional dose will be one of seven approved (or pending) vaccines. ): Oxford-AstraZeneca and Pfizer-BioNTech, Moderna, Novavax, Valneva, Janssen and Curevac.
What is the third dose for
But will the third dose of the vaccine be really necessary? Most experts around the world believe they are, but when to administer it remains the unknown. very likely that a third dose of the vaccine will have to be done – he adds Sergio Abrignani, who is also a member of the CTS – but at the moment we do not know whether against a different variant and we do not know when, perhaps in the fall, more likely at the beginning of next year.
There are two variables to keep an eye on that could make the booster necessary, the third dose: thearrival of variants capable of evading the immune response induced by the vaccine (at the moment the products in use are effective, albeit slightly weakened with some strains in circulation) and duration of immunity. For most vaccines there is always a need for a booster – explains Abrignani – but usually the duration of immunity is studied before putting the product on the market, so as to know when to proceed with the booster. Now we are in an emergency and we are studying in the field. At the moment we do not know how long the immune response lasts, we see that there is a high protection even 8-10 months after the end of the vaccination cycle, but a booster may be necessary later to “Refresh” the immunological response or for cI’ll show an emerging variant, even if a good response against the original strain persists. Even against the Indian? As for the Indian variant, which is being talked about so much – concludes the immunologist – we know from the data coming to us from the United Kingdom that after a single dose you are not protected from the disease, but in any case you get sick in a not very severe way. With two doses, on the other hand, you are protected in an important way. Now we still don’t know if we will have to make a call against the Indian variant, maybe even just to avoid the mild disease.
May 31, 2021 (change May 31, 2021 | 11:57 am)
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