The vaccine from Oxford and AstraZeneca could have a substantial effect too on transmission of the virus. Analysis of the latest data from three different Phase 3 trials suggests the vaccine recently authorized by the EMA reduces the number of positive swabs in vaccinated individuals by 67%, potentially also reducing the asymptomatic passage of the virus between vaccinates and their contacts. A feature that could have a major impact on the pandemic, because if the results were confirmed, every person immunized it would indirectly protect even those around her. These are preliminary data, but it is the first time that the efficacy of a vaccine has also been confirmed in reducing transmission (and not only in protecting against the disease with symptoms).
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Space out the doses. But the results of the trials, which are currently under review before being published on the Lancet, suggest another interesting fact, namely that the first dose of the Oxford vaccine already confers an average protection of 76% against symptomatic infections, starting three weeks after the injection and up to 90 days thereafter. For three months there is therefore a high efficacy that does not seem to diminish, coverage that reaches 82% when the second dose is also administered, provided it is more than three months after the first. This is a much higher protection than that which emerged from the interim analyzes, the interim evaluations that served for the conditional authorization of the vaccine.
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The article suggests that the efficacy of the covid vaccine with symptoms increases from 55% when the second dose is given no more than 6 weeks after the first, to 82.4% when it arrives more than three months. after. An effect that seems strange only to non-experts: even vaccines against some forms of influenza and against Ebola are more effective if carried out on more distant occasions. The increased long-term protection afforded by other depotentiated adenovirus vaccines, like that of Johnson & Johnson, gave hope it could be so.
some doubts. However, as the Guardian, some scientists remain skeptical of the results and point out that the trial was not designed to compare different dosages, and some variables that were not “weighted” on different sample samples may have influenced the final data. For example, single dosing was given more often to young subjects, more often to women, more frequently to health workers and whites.
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If the results of the study are confirmed, it would be reassurance for the vaccination strategy undertaken by the United Kingdom, which has chosen to start giving a dose of the vaccine to as many people as possible and take the risk of delaying the boosters. Given this double discovery (cutting transmissibility and higher protection by delaying the second dose), as vaccinates increase, infection levels could decrease faster than hoped. Provided that the variants of coronavirus do not get a hand. The tactic starting with a single dose, supported by some scientists in the UK and beyond, had been heavily criticized for the lack of supporting scientific data.
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All that remains is to wait. In the UK it is being administered also Pfizer-BioNTech’s vaccine, whose impact on viral transmission is not known. This vaccine should be given in two doses 21 days apart, to obtain 95% protection. The effects of the massive vaccination campaign in the Channel beyond should begin to be seen within a few weeks: according to BBC, one in six British citizens has been vaccinated.
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