Rome, 8 June 2021 – We have all asked ourselves in these months of vaccination campaign, but it is even more felt now that we are approaching summer and it is possible that we are leaving for one holiday long awaited with only the first dose of Covid vaccine. So: after how many days from the first dose you are protected, and to what extent, by the risk of contracting the disease?
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Let’s start with the vaccine Johnson & Johnson which unlike the other three involves only one inoculation. So in this case we have more certainties. Aifa (the Italian Medicines Agency) explains in its Faq on this point: “Protection with COVID-19 Vaccine Janssen begins approximately 14 days after vaccination. “
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For the other three vaccines (Pfizer, Modern and AstraZeneca) we must distinguish between the guaranteed protection after vaccination is completed (therefore with the two doses) and that guaranteed – albeit to a lesser extent – after the first dose only which however guarantees a protection rate. He tells us in the Faq, the Higher Institute of Health: “Although, according to the first data found from the current campaign, even after the first dose it is likely that there is some protection from the virus, this is not immediate after inoculation of the vaccine, but it develops progressively after at least 7-14 days from the injection. “So the first response is that in any case protection begins to develop at least one week after the first dose.
That said, the “coverage” rate from the first dose of each individual vaccine. But we can refer to studies that in the United Kingdom have taken into consideration the two types of vaccine: those with messenger Rna and those with viral vector. In particular Pfizer e AstraZeneca. But which can also be used for Modern (Rna messenger) e Jonhson & Johnson (viral vector). Well, according to these studies, which the prestigious Bmi (British Journal of Medicine), the first dose would develop its full effectiveness after 28 days. Although, as we have seen, it begins to produce its effects already after a week.
Second question: can we determine what the effectiveness rate of the first dose? We can always rely on the studies published by the BMI, according to which (we always refer to Pzifer and AstraZeneca) after the first dose the possibility of contracting symptomatic Covid is reduced by 60-70% and that of contracting an infection that leads to hospitalization of 80%. Johnson & Johnson’s efficacy was estimated at 66.9% for symptomatic disease and 85.4% for severe infections.
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