May 17, 2021

First independent review for a COVID vaccine gives the Oxford vaccine up to 90% effective

The scientific journal The Lancet has published on Tuesday the first results of a vaccine against the coronavirus that have passed a peer review. They correspond to the one created by the Anglo-Swedish laboratory AstraZeneca and the British University of Oxford and confirm the already known data of its phase three: the vaccine has an efficacy of 70%, which reaches 90% when a half dose is inoculated followed by one complete one month later. With two whole doses, the efficacy is 62%. The analyzes so far suggest that the efficacy is higher in the half-dose group compared to the full one, regardless of factors such as age – a matter that generated controversy after the first reports on its efficacy – but the authors will have to continue studying these data.

An error in the dose that ended in good luck: this is how the AstraZeneca and Oxford vaccine reached 90% efficacy

An error in the dose that ended in good luck: this is how the AstraZeneca and Oxford vaccine reached 90% efficacy

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According to The Lancet, data from the Oxford vaccine show that it is safe. Only three of the 23,745 participants – in trials in the UK, Brazil and South Africa – have suffered “adverse events” that could be related to the vaccine, one of them in the group that received the placebo, another in the group that did receive the vaccine. –It is a case of transverse myelitis– and a third person, with high fever, whose group he belonged to has not been made public. All are recovered or in the process of doing so. In all, 175 “adverse” events were detected, but the other 172 were not related to coronavirus or vaccine control.

To analyze the efficacy, the researchers looked at the number of COVID-19 positives with symptoms (fever, cough, shortness of breath, loss of smell …) developed among participants who had received two doses of the vaccine compared to the placebo group, taking into account only those cases that occurred at least 14 days after receiving the second dose within 11,636 participants from the United Kingdom and Brazil. There were 131 cases of COVID-19 with symptoms, 30 among vaccinated people and 101 in the control group. Of those 30 individuals, 27 had been inoculated with the dose standard and 3 with a lower amount the first time.

The scientific publication details that the subsample of people who received first half a dose and then a full one was 1,367 people in the United Kingdom (the group consisted of more than 2,700 in total, adding those who received a placebo), and that it was due to “differences” in the measurement methods between the vaccine samples. Within this group there were no volunteers older than 55 years, because the half dose was given at an early stage of the trials and the introduction of older people into the studies was done later.

At the request of the journal’s reviewers, the researchers explored whether the difference between volunteers who received the standard dose and those who received less is due to the amount or other factors, such as age or the period between vaccination. The analyzes at the moment suggest that efficacy is higher in the second group regardless of age or time between doses, but this is not a conclusive question and they will have to continue collecting data, according to The Lancet.

Regarding hospitalizations, 10 out of 23,745 volunteers were counted –only the admissions that occurred after 21 days after the first dose were taken into account–, all within the group that received placebo. Two were considered serious cases, one of which died.

The pending task: study more data from people over 56 years old

According to The Lancet, most of the 23,745 participants in the study were between 18 and 55 years old (82%), so the researchers want to delve into future analyzes in the case of people over 56. Other one of the pending tasks will be to find out how long the protection lasts, since the first trials began in April of this year and all infections have occurred less than six months after the first application.

The project promoted by Oxford and AstraZeneca is based on a different technology than the two mRNA vaccines from Moderna and Pfizer, whose vaccination began this Tuesday in fifty hospitals in the United Kingdom. In a simplified way, it is made from a weakened version of a chimpanzee common cold virus modified so that it cannot grow in humans and into which the gene for the protein S present in the coronavirus is introduced. It is a vaccine that can be stored in standard refrigerators, while Pfizer’s requires temperatures between -70 ° C and -80 ° C.


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