Another success for the COVID-19 vaccine? The candidate can also prevent further transmission of the coronavirus | Sciences



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An artist’s illustration of the adenovirus used in a COVID-19 vaccine from AstraZeneca and the University of Oxford.

AstraZeneca

By Jon Cohen, John Travis

SciencesThe COVID-19 reports are supported by the Pulitzer Center and the Heising-Simons Foundation.

A third vaccine candidate for COVID-19 has compelling evidence that it works, and may be easier to distribute and cheaper than the other two vaccines that have already been shown to protect people. Developed by the AstraZeneca company in partnership with the University of Oxford, the vaccine was an average 70% effective in preventing the disease, the developers announced today in press releases. In a dosing schedule, its efficacy was 90%, based on the results of interim analysis of data from clinical trials.

AstraZeneca says that around 3 billion doses of the vaccine could be ready by 2021. While the seemingly powerful COVID-19 vaccines recently announced by Moderna and the Pfizer / BioNTech collaboration are based on a fragment of messenger RNA that encodes the protein. peak surface area of ​​SARS-CoV -2, the AstraZeneca / Oxford vaccine stimulates immunity by using a crippled chimpanzee adenovirus as a “vector” to deliver the spike gene. (A Russian team has also presented evidence that their vaccine works, but noticed too few COVID-19 cases at the time to persuade many outside scientists.)

The AstraZeneca-Oxford collaboration is tracking more than 23,000 vaccinated people in the UK and Brazil. It reported a total of 131 COVID-19 cases in two groups: 8,895 people who received two full doses one month apart and 2,741 people who received half the dose first followed by the full dose. The first scheme was only 62% effective, a clinical trial measure that may not exactly translate into the real world. But in the second, the efficiency jumped to 90%. The collaboration did not report the breakdown of cases between people in the vaccine arm of the trial and the control group. It also did not provide any data on COVID-19 protection among the elderly or various ethnicities.

Peter Piot, director of the London School of Hygiene and Tropical Medicine, says he was “very pleased” to see these results, especially given the “encouraging news” that the half-dose scheme worked better, meaning more people they could receive the vaccine while it is still in short supply for the next few months. But he noted that none of the COVID-19 efficacy results reported to date have offered much data. “It is frustrating that all these announcements are made through press releases and we cannot review the actual data,” says Piot. Without knowing how the 131 cases are divided between the different vaccine regimens and the people in the control group (who received a meningococcal vaccine or a placebo), the researchers cannot calculate what is known as the confidence interval around the reported efficacy. “We desperately need full transparency about the trials and the data,” says Piot.

Even if people who receive the COVID-19 vaccine become infected with SARS-CoV-2, the injections can protect them from serious symptoms. There were no hospitalizations or serious cases of COVID-19 in vaccinated participants, AstraZeneca and Oxford reported. They also said that vaccinated people had fewer asymptomatic infections, suggesting they were less likely to transmit SARS-CoV-2 to other people.

So far no serious safety concerns have emerged in efficacy trials, says AstraZeneca. The company now plans to apply for emergency use of the vaccine to regulatory bodies in the UK and other countries. Other vaccine efficacy trials involving 60,000 participants are underway in the United States, Kenya, Japan, and India.

The company says the vaccine, which only requires standard refrigeration, can cost between $ 3 and $ 4 per dose. Moderna, on the other hand, can charge $ 25 or more per dose, according to statements by its CEO. Your vaccine and that of Pfizer / BioNTech require freezers for storage and transport to prevent the RNA and the lipid particle that contains it from degrading.

“These results suggest that it is very effective in protecting serious diseases and may reduce transmission,” said Charlie Weller, head of vaccines research at the Wellcome Trust, in a statement. “It is based on established vaccine technology, which does not require challenging cold chains and, therefore, should facilitate implementation and global access. As with all interim results that we have seen, it is critically important that the test is completed and that regulators can now independently and rigorously evaluate the data. “

Adrian Hill, who led the team at Oxford University that developed the vaccine, says there are many theories but little evidence to explain why the half-dose prime injection worked better. He says that “perhaps the most likely and measurable explanation” is that people develop an immune response against the chimpanzee virus vector that attenuates the impact of the booster vaccine. In theory, a half dose up front would trigger a milder response against the vector.

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