“What the United States is launching is a gigantic field trial. We must be optimistic, but we must take into account that they have vaccinated 10 times more than we have vaccinated”. Thus the virologist Francesco Menichetti, head of infectious diseases at the hospital of Pisa, comments on the new guidelines of the Centers for Disease and Prevention (Cdc) USA to the Adnkronos Health, which provide for the fully vaccinated to return to normal life in full, without masks or social distancing. “The US initiative – underlines Menichetti – is based on the assumption that the vaccine effectively cuts down the transmission of the virus, that is, it not only prevents the disease, but cuts down the contagion or involves a contagion that is not clinically significant. It is a plausible assumption – he admits as a virologist – even if he does not have such well-established and consolidated evidence that would be necessary “. For this, he adds, “it is a decision that in my opinion is questionable.” “The anti-Covid vaccine with an adenoviral platform such as AstraZeneca or Johnson & Johnson can lose efficacy due to the antibodies that are produced against the adenovirus. Hence the hypothesis of making calls with vaccines with different platforms, messenger Rna, can make sense. Also in this case we take note of experiments that are important, but they are preliminary “, said Menichetti, commenting on a British study that certifies the safety of the AstraZeneca mix. -Pfizer for the first and second dose. “However these are effective vaccines capable of soliciting either the first response or the immunological memory, therefore – underlines Menichetti – in a secular way I would neither recommend nor advise against it”. But if anyone who took the first dose of AstraZeneca had reservations about the booster, “making it clear that the second dose is absolutely no more dangerous than the first and that if you haven’t had any problems it can be done safely, I believe that, with the same interval at 3 months, could also access an mRna vaccine. This however – he specifies – will depend on the availability of vaccines and the policies to be implemented. But – notes the virologist – General Figliuolo, although military, seems to me to be demonstrating great flexibility. And therefore – concludes Menichetti – if there were the possibility, I would not be scandalized nor would I feel like drawing the red card “.