Deciding to administer the second dose of coronavirus vaccine with a different preparation from the one used at the first injection is not a problem from a medical point of view, indeed, in some cases it could be even better.

The first studies

The first studies on the so-called Anti Covid «vaccine mix», a practice that could help countries struggling with dose shortages or stalling vaccination campaigns with immunization. Recent Spanish research (we covered it in detail here) monitored 670 volunteers aged 18 to 59 who had already received a first dose of AstraZeneca (a viral vector vaccine) and who subsequently had Pfizer (vaccine). to messenger RNA): the side effects were not different, or more or less serious and frequent, on the other hand, the mix appears to have increased and enhanced the antibody response.

The potential to function well

“It was expected that using different vaccines would work well, because anyway all vaccines we are using they target the same protein (the so-called «spike», ed). The technology that helps the vaccine to enter cells may eventually change, as happens between AstraZeneca and Pfizer, ”explains Antonella Viola, immunologist and professor of Pathology at the University of Padua. The combinations between preparations would therefore all possible and also the order of administration between one and the other vaccine could be exchanged as needed. However, these are deductions made on the basis of scientific assumptions that still need confirmation from specific studies.

The Covid-19 situation in Italy and in the world

When is it even better?

In the case of vaccines (such as AstraZeneca) based on a viral vector (in this case an adenovirus), think about a second dose with vaccines designed with messenger RNA technology it could be even better, given that some people can develop a immune response against adenoviruses that could weaken the effectiveness future of the drug. “In a purely theoretical line, a mix of vaccines with a first dose AstraZeneca and the second based on mRNA would be better – confirms the expert -, because AstraZeneca also works by inducing an anti-adenovirus response, while the messenger RNA used by Pfizer causes only the specific anti-Covid response “.
In Italy in which cases it would help to decide for the vaccine mixture? “It could solve the problem of people who give up AstraZeneca, which, although in small numbers, are there: also because the final goal is not to force the population to vaccinate, but to have the maximum possible coverage”.

May 26, 2021 (change May 26, 2021 | 09:32)


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