There are those who, over 60, faced with the prospect of taking a second dose of vaccine different from the one already done, prefer to drop it and not show up at the reference hub. And there are those who, under the age of 60, are torn by doubt: do Pfizer instead of AstraZeneca for the recall, or insist with the latter ?. Finally, there are those who book and then do not show up at the last moment because they are convinced that the first injection is more than enough to protect them from the risk of contagion. The result, especially for people aged 60 and over, can be seen in hospitals: because the new Covid patients are precisely the no vaxes, or those who decide not to do so.
But what does it mean, in terms of coverage from the virus and the consequences it generates, to stop at a dose of vaccine? For Fausto Baldanti, virologist, head of the molecular virology laboratory of San Matteo, “in this case the risk is around the corner”. “The reason is demonstrated by England, which vaccinated everyone, allowing six months to pass from the first to the second injection, and found itself having to manage an important increase in cases”. The coverage that the first dose guarantees from the infection is estimated at around 70% three weeks after inoculation. “This is the estimate, in fact, but in real life the percentage could be lower – explains Baldanti – let’s say that the possibility of contagion ranges from 30 to 40%, and concerns almost all vaccines. The only one who seems to give protection with a single dose is Johnson & Johnson ”.
Given that, as the scientific world confirms, “a single dose of vaccine is not sufficient to guarantee total protection from contagion”, to rest assured you must absolutely bet on two. “It is only with the assumption of the second that all the parameters are grouped towards high values - assures the virologist of San Matteo – not to mention the fact that an incomplete vaccination can favor the proliferation of variants, especially Beta (formerly Indiana), the latest arrival, and quick to supplant also the Alpha (ex English). But, it should be noted, that in reality total protection is not achievable because it is not a sterilized vaccination: about 1% of those who have done two doses can be infected and 1 in 2,000 can be contagious. What we can achieve when we undergo the recall is to achieve 95% protection. “
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For those under 60, especially middle-aged, who have experienced AstraZeneca because they are part of categories, such as school staff and law enforcement, on which the Anglo-Swedish vaccine was previously used preferentially, a difficult dilemma has arisen. to be solved on the spot. Because they are advised to have heterologous vaccination (two different doses), but recently they have seen a new possibility open up: to go back to AstraZeneca, but taking responsibility for it. So what to do? What would happen if they opted for the heterologous? “There is no reason not to imagine that the vaccine response cannot be achieved with two different doses of vaccine – emphasizes Baldanti – only one doubt remains: the side effects. It is true that the studies on the subject are limited, but a recent one, Published on Lancet, analyzed 800 people vaccinated with four different vaccine combinations: the first AstraZeneca-Pfizer, the second Pfizer-AstraZeneca, the third Pfizer-Pfizer, and the fourth AstraZeneca-AstraZeneca. And it emerges that with the last two combinations the side effects increase. Because, given that the reactions to the vaccine are normally more marked after the first injection and milder or non-existent with the second, in the case of taking different vaccines, it would be like doing the first dose twice “.
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However, we are talking about side effects that are not long lasting. It is necessary to distinguish between males and females: in the former they are less present, in the latter, in fertile age, more marked. They are more or less transversal side effects to all vaccines: fever, migraine, soreness, fogging and weakness. “Let’s say that they are classic effects, but none of the 800 patients examined in the study in question needed hospitalization – continues the expert – it must be said, however, that this research has two limitations: it only analyzed 200 patients for a combination of vaccines and was only conducted on people over 50.
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One of the claims conveyed by the media and social networks, so much so that it is prevalent at this time, is that heterologous vaccination covers longer from the possibility of Covid infection than that done with the same vaccine. “In reality, the effectiveness of the two vaccinations is equal – assures Baldanti – the responses of the immune system are comparable. How long does it last? It is difficult to quantify it. Nine months? Will it last even longer, and vaccination does not necessarily have to be done. every year because they are vaccines that deeply stimulate the immune system “.
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Since being immunized from Covid means being protected for a long time, it would be better to check the level of antibodies in the blood. And do it periodically to establish its duration over time. “We should begin to evaluate this possibility and transform it into a structured discourse – concludes Baldanti – therefore, in this way we could evaluate whether or not there is an organism response to the vaccine, while verifying the effectiveness of the method. it is about establishing guidelines, as is done for other vaccines. Let’s remember that at the beginning of this pandemic there were those who said that the antibodies would only last two weeks … “.
