Will we need a third dose of Covid-19 vaccine?

Will we need a third dose of Covid-19 vaccine?
Will we need a third dose of Covid-19 vaccine?

Likely, which is why studies in the field are proceeding. But much will depend on the evolution of the virus and the pandemic, as well as on the duration of the immune response

(foto: Spencer Davis on Unsplash)

A, due, maybe three. And so on, every year. There question doses has been more central than ever when it comes to Covid vaccines. Always. Leaving aside the technical issues – you will remember the possibility of extract more doses from the vials of vaccine – the number of doses was central in the discussions of strategy ed vaccination efficacy. Starting in the United Kingdom, with the choice of mass vaccinating the highest number of people with a single dose initially, up to the evidence regarding efficacy against variants (and it seems, for example, a double dose make a difference against the delta variant (B.1.617.2, a strain of the variant sequenced in India).

So, while now the campaign is in full swing with us too, with the latest openings, regardless of age group or category, for some time now we have begun to look to the near future. Basically we are already talking about one possible third dose (except for Johnson & Johnson, the only one at the moment to foresee one instead of two), to mean more generally a recall vaccinal. Will it help? Every year? The answer is very vague, but the practically shared idea is that it is possible and that we must prepare.

Big Pharma knows this well, and for some time. Only in January, in fact, shortly after his approval vaccine, Modern for example, he announced that he was working on an experiment to understand if a third dose of his product, a booster, could increase its effectiveness, especially in the fight against the emergence of new variants. In fact, the node variants, together with the question mark or on duration of immunity conferred by natural infection and vaccine, are the central themes in discussions on the usefulness or otherwise of a booster, with identical or updated versions of the vaccine, or targeted to combat variants more specifically. A vaccine that uses the genetic information of the variants for the production of the spike protein against which to direct the immune response, easily and rapidly adaptable, especially with the technology of mRna products. This is what the Moderna company did, launching a trial with a specific vaccine for beta variant B.1.351 (discovered in South Africa), which according to the results released only a few weeks ago is able to enhance the immune response against variants.

The other great enigma facing the need for one (or more) possible reminders, has to do with the duration of immunity acquired after the vaccination (and more generally after exposure to the coronavirus). The studies accumulated so far have produced somewhat different data, but lead to believe that immunity acquired after infection, albeit with some variable from person to person, decreases over time but lasts in general. at least some month, you’re about even with vaccines, maybe years, although it’s not entirely clear what level of immune response is needed to ensure protection.

The publication of a recent study on the subject, which noted the presence of cell they produce antibodies almost a year after his recovery, he argues in favor of the existence of avery long-lasting immunity, due to the presence of long-lived cells, capable of producing antibodies against the coronavirus potentially for life. Whether this is sufficient to provide protection, again, is unclear.

And that’s what they are for Education, e data. It is in this direction that the initiative of the UK which has just launched a study to understand if and how much a third dose of anti-Covid vaccine (other than those tested) helps to boost the immune response. Combining several, considering that the booster, the third dose could be different from those previously received. However, attempts are also underway combination with others vaccines. Pfizer, for example, has just announced plans to administer the third dose of its Covid vaccine together with that against pneumococcus in adults over 65.

The preparations are essentially already in place, as required, as commented, among others, by the US expert Anthony Fauci questioned on the subject. Would be “fool” don’t do it, he said, even considering the climate of uncertainty in which we find ourselves. Faced with the uncertainty about the duration of immune responses to natural infection and the vaccine, there are also those concerning theepidemiological evolution of the pandemic, with the diffusion of variants and their ability to evade vaccines or not.

With several now approved, and even with studies still in progress, there are those who are unbalanced to imagine the type of booster that we may receive. For example Nathan Bartlett, expert on respiratory infections of the Newcastel Universiy, on the pages of The Conversation, explained how difficult in the long term, if requested, the solution will be to resort to AD vaccines adenovirus (like Astrazeneca or even J &). Not just for the rare bleeding problems associated with vaccines, but because repeated cycles in fact with adenovirus products risk becoming more and more less effective, because the immune system also responds to adenovirus, interfering with the ability to release the genetic material needed to assemble the answer against the coronavirus.

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