Thu. Oct 21st, 2021

The vaccine from the pharmaceutical company AstraZeneca and the University of Oxford reduces the transmission of the coronavirus. According to a study by both institutions that has not yet been validated by independent scientists, the follow-up of those vaccinated suggests a significant reduction in the ability to infect. Just as striking is another result: by spacing the administration of the first and second doses up to three months, the efficacy of the inoculate remained in the interval.

This study appears the same week that many European countries study not to administer the compound to those over 65 .

The Oxford researchers and the pharmaceutical company have published the latest results from their four ongoing studies (two in the UK, and others in Brazil and South Africa). The work adds one more month of data to those already published last November and details new data observed over time.

Perhaps the most prominent is the impact of the vaccine on the ability of the virus to maintain its contagion capacity. Based on weekly monitoring, using samples obtained from volunteers in the UK, the authors suggest that the potential for transmission of coronavirus was reduced by 67% after the first dose.

The series of trials is not designed to measure how much the vaccine affects transmission of the virus. But the weekly follow-up of the participants has made it possible to estimate it. In principle, an effective vaccine should mitigate the severity of infections or make them asymptomatic, but without changing the rate of positive CRP.

But what they have verified with the repetition every week is that the positive CRPs were reduced by up to 67% after the first dose and almost 50% after the second.

“We have not measured transmission in a specific way, because this requires a different type of study. What we have is a study that shows us the number of people who are no longer infected. And if they are not, the logical presumption is that they can no longer transmit the virus, ”said Andrew Pollard, the scientist in charge of the vaccine study at the University of Oxford.

In an interview with the BBC, the British Government Secretary (Minister) for Health, Matt Hancock, said: “Now we know that the Oxford vaccine also reduces transmission and that will help us all to get out of this pandemic,” according to picked up The New York Times .

Another of the results of this work, which the medical journal The Lancet is reviewing , has to do with the interval between one dose and another. When we went from the experimental phase to the generalized administration of the vaccines already commercialized, the recommendation was to space the two punctures about three weeks apart.

That period, used in the trials, seemed adequate to activate the defenses of the immune system and not too long for the virus to find escape routes due to the selective pressure.

But science ran into public health policy here. Encouraged by some very preliminary results, the British authorities (followed later by those of other countries) decided to space the administration of the second dose beyond 21 days, so they had more vials for the first dose.

The decision involves risks, since it could facilitate the virus to mutate by finding weak points in the immune system of the vaccinated environments. In any case, the World Health Organization has recommended not allowing more than six weeks to pass.

The Oxford and AstraZeneca study ran into a problem: They weren’t able to produce all the vaccines they needed to follow the initial two-dose schedule. So they lengthened the administration of the second to a subset of the volunteers. And they turned the problem into an opportunity to validate the separation between doses.

Their results now suggest that the efficacy of the vaccine improves over time. They show that this increases from 54.9% when the interval between the first dose and the second is less than six weeks to 82.4% when 12 weeks are spaced.

This temporal separation has allowed them to verify that protection is maintained at 76% up to 90 days for those who were only vaccinated once, losing only six percentage points compared to the double dose regimen.

Professor Pollard said in a note: “These new data offer important validation of the interim data used by more than 25 regulators, including the MHRA and the EMA [British and European medicine organizations, respectively], to grant authorization for emergency use of the vaccine ”.

The British scientist, co-author of the study, also assured that his results supported the recommendation of the British authorities to space out the administration of the two doses, thus reaching more people with the available vaccines, “confirming that people are protected from the 22 days of a single dose of the vaccine ”.

But they also acknowledge that more research needs to be done to see if there are long-term immunity differences between getting an injection or two.

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