Monday, June 27

Pfizer Vaccine Is 91% Efficacy For Up To Six Months, Trial Shows | Coronavirus


The coronavirus vaccine developed by Pfizer and its German partner BioNTech protects against symptomatic Covid for up to six months, according to an updated analysis of clinical trial data.

In a statement issued Thursday, the companies reported 91.3% efficacy against any symptoms of the disease in participants tested up to six months after their second injection. The level of protection is only marginally lower than the 95% achieved shortly after vaccination.

The findings are the first to show that the vaccine remains effective for many months, a result that doctors and scientists desperately waited for because it suggests that people who get vaccinated now should be protected at least until the fall, when boosters may be ready.

Analysis of participants in the phase 3 trial, which has enrolled 46,307 people, identified 927 symptomatic Covid cases. Of these, 850 were in the placebo group of the trial and 77 in the vaccine group. There were 32 cases of severe Covid, as defined by the US Centers for Disease Control and Prevention (CDC) in the placebo group, and none in the vaccinated group. More than 12,000 vaccinated people in the trial have been followed for at least six months after their second dose.

Even more surprising are the results from the South African arm of the trial, where nine cases of Covid were observed among 800 participants. All of the cases were in the placebo group, and six were confirmed to be the new “worrying variant,” B.1.351, which has concerned scientists because of its ability to partially evade antibodies produced in response to past vaccines or infections. Public Health England said Wednesday it knew of 469 confirmed or probable cases of the South African variant in the UK.

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Fast guide

How does the Pfizer / BioNTech Covid-19 vaccine work?

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The Pfizer / BioNTech Covid vaccine is an mRNA vaccine. Essentially, mRNA is a molecule used by living cells to convert the sequences of genes in DNA into proteins that are the building blocks of all its fundamental structures. A segment of DNA is copied (“transcribed”) into a fragment of mRNA, which in turn is “read” by the cell’s tools to synthesize proteins.

In the case of an mRNA vaccine, the mRNA of the virus is injected into the muscle and our own cells read it and synthesize the viral protein. The immune system reacts to these proteins, which by themselves cannot cause disease, as if they had been transmitted by the entire virus. This generates a protective response that studies suggest lasts for some time.

The first two Covid-19 vaccines that announced the results of the three phase 3 trials were based on mRNA. They were the first to get out of the blocks because, as soon as the genetic code of Sars-CoV-2 was known, it was published by the Chinese in January 2020: companies that had been working on this technology were able to start producing the virus mRNA. Making conventional vaccines takes much longer.

Adam Finn, Professor of Pediatrics at the Bristol Children’s Vaccine Center, University of Bristol

Since the cases in the South African arm of the trial are so low, more evidence is needed to confirm the vaccine’s protection against the new variant, but the scientists were still delighted with the result. “I see this as a really positive indication,” said Danny Altmann, professor of immunology at Imperial College London.

He said scientists had become “terribly concerned” about the variant’s ability to evade immunity from a previous infection or vaccination. “Studies like this confirm our feeling that the vaccine offers such a great margin of protection that even with some loss of immunity, it is still safe,” he said.

Pfizer Chairman Albert Bourla said the latest data puts the company in a position to apply for full approval of the vaccine from the US Food and Drug Administration. The jab is currently approved under authorization for use by Pfizer. emergency.

The results came as reported by scientists in the UK. strong immune responses in older people who had received two injections of the Pfizer vaccine. Blood tests in 100 people between the ages of 80 and 96 revealed that 98% produced strong antibody responses after two doses of the vaccine given three weeks apart. Antibody levels more than tripled after the second shot.

The results, released in a prepress which has not yet been peer-reviewed, will increase confidence that the Pfizer vaccine can be highly effective against Covid even in the most vulnerable older people, who tend to elicit much weaker immune responses to both vaccines and natural infections. Pfizer tested its vaccine with a three-week gap between injections, but the UK leaves a three-month gap, meaning it is unclear whether the same level of protection is achieved.

Paul Moss, a professor of hematology at the University of Birmingham, who led the study with Dr. Helen Parry, also in Birmingham, said the team was surprised and very pleased to see the results, which were consistent with “excellent clinical protection.” from Pfizer. the vaccine seems to provide. The first large real-world study of the Pfizer vaccine in Israel found that two injections prevented 94% of symptomatic cases in all age groups.

The scientists went on to examine another branch of immune defenses elicited by the vaccine, known as the T-cell response. Antibodies protect against infection by engulfing the virus and preventing it from infecting cells, but T cells destroy human cells that already they are infected and can also support antibody production over time. After both injections of the vaccine, two-thirds of the participants had detectable T-cell responses. “We know that as people age, their cellular immune responses are more difficult to elicit,” Moss said. “So that’s something we will have to watch very closely.”

Additional work in Public Health England’s Porton Down laboratory showed that blood serum drawn from volunteers after two vaccine injections strongly neutralized the original coronavirus that spread around the world last year. But it was on average 14 times less effective against the P.1 variant that was first seen in Brazil, and has now reached the UK and elsewhere.

“The Brazil variant reduces the neutralization response, but at this early post-vaccine stage, where we are seeing such high levels of antibodies, we are still confident that this should provide valuable protection against this variant of concern,” Parry said.


www.theguardian.com

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