Researchers are conducting Phase 3 trials of the University of Oxford/AstraZeneca vaccine candidate in several thousand volunteers in the U.K., South Africa and Brazil, such as at this testing laboratory in São Paulo.
Photo: amanda perobelli/ReutersThe prospects of successfully developing a coronavirus vaccine as soon as this year were buoyed Monday when three of the world’s leading candidates reported positive early trial data.
Vaccines being developed by University of Oxford researchers and AstraZeneca AZN -3.47% PLC; Pfizer PFE 0.95% Inc. and German partner BioNTech BNTX 4.36% SE; and China’s CanSino Biologics 6185 2.17% all reported fresh updates showing their shots generated immune responses and were safe to use.
The results cement the trio’s position among a few drugmakers and institutions at the vanguard of the race to develop a Covid-19 vaccine. About 160 vaccines are in development, including about 20 that have started human testing, according to the World Health Organization. With a clutch of front-runners now having reported positive early results, attention is rapidly turning to larger, later-stage trials that would prove the efficacy of the shots in tens of thousands of volunteers and potentially lead to the treatments’ approval for use.
For the Oxford vaccine, a study of 1,077 healthy adults showed the shot produced two kinds of immune response that could defend a body against Covid-19, according to results published in the Lancet, a British medical journal. The vaccine caused no serious side effects, the study found.
The early but promising Phase 1-2 results mean researchers remain on their schedule to have the shot—described by the WHO’s chief scientist last month as the world’s most-advanced vaccine candidate—ready for mass production as soon as September.
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Separately, Pfizer together with BioNTech on Monday announced early positive results from a trial in Germany, which supported results from a corresponding U.S. trial. The pair said the small study of 60 patients showed their lead vaccine candidate led to high levels of antibodies for coronavirus, although some study subjects had flulike symptoms and injection-site reactions.
However, the most advanced results to date for an experimental coronavirus vaccine were published Monday in the Lancet, for the second study of a shot codeveloped by CanSino Biologics and the Beijing Institute of Biotechnology. It was the first time that a stand-alone phase 2 study for a coronavirus vaccine had been published in a peer-reviewed journal.
The study of more than 500 volunteers found the vaccine was safe and induced significant immune responses in the majority of people after a single shot. Some people receiving the vaccine experienced fever, fatigue and injection site pain, most of which were mild or moderate, the researcher said.
Still, all three vaccine candidates updating Monday remain unproven. All, though, are poised to enter large-scale clinical trials designed to show whether the shots safely protect people from Covid-19, which could begin to yield answers in a few months. Positive results could support the availability of initial doses by the end of this year.
Researchers for Oxford are already conducting much wider Phase 3 trials of several thousand volunteers in the U.K., Brazil and South Africa, with a trial for 30,000 people in the U.S. scheduled to begin in August.
The Pfizer/BioNTech vaccine also is scheduled to begin a major U.S.-based clinical trial by the end of this month, as is another candidate co-designed by Moderna Inc. and the National Institutes of Health.
CanSino researchers also have said, alongside Monday’s data, that they plan to start a Phase 3 study as soon as possible. One potential issue with the CanSino vaccine, however, is that it incorporates a different virus, an adenovirus, that serves as a sort of carrier for the portion of the vaccine that is intended to trigger an immune response against the coronavirus. Some participants in the study had pre-existing immunity to the adenovirus, which seemed to mute the immune responses against the coronavirus. Researchers said it might be necessary to provide an additional dose to people with pre-existing immunity to the adenovirus.
Advances come as various governments are jockeying to secure vaccine supplies. The U.S. is providing funding for several, including Oxford’s. In May it agreed to pay AstraZeneca, which is making and distributing the shot, $1.2 billion to secure at least 300 million doses. The company, which also has supply deals with other countries, is committed to making 2 billion doses, with perhaps 1 billion available this year.
The University of Oxford/AstraZeneca vaccine has been described by the World Health Organization’s chief scientist as the world’s most-advanced candidate.
Photo: douglas magno/Agence France-Presse/Getty ImagesThe Oxford/AstraZeneca results published Monday studied 1,077 adults in the U.K. from ages 18 to 55 who had no history of Covid-19. About half the participants were given the new vaccine, while the other half was a control group given a meningitis vaccine. Researchers found that participants given the Covid-19 vaccine had significant immune responses for both antibodies and T-cells. The Oxford vaccine uses a similar method as CanSino’s, but with a key difference: It uses a virus from a chimpanzee because humans are less likely to have a pre-existing immunity to it.
Antibodies are proteins produced by the immune system that bind to proteins on a virus and can trigger a process that neutralizes the virus. The vaccine’s antibody response peaked by day 28 and remained high for the duration of the study, which covered the first 56 days of the continuing trial.
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T-cells are white blood cells that can coordinate an immune response and destroy cells that a virus hijacks. These T-cells may have a memory that can recall a virus, theoretically providing long-term protection. The Oxford researchers found favorable T-cell responses peaking 14 days after vaccination and declining slightly by day 56.
Researchers found that the Covid-19 vaccine produced only minor side effects that could be alleviated by acetaminophen, the active ingredient in Tylenol. About 70% of the people who got the Covid-19 vaccine reported fatigue, and 68% reported a headache.
The study’s authors said that they require further clinical studies, including in older adults, to see whether the vaccine protects against infection because the results published Monday focused on immune responses measured in a laboratory.
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“There is still much work to be done before we can confirm if our vaccine will help manage the Covid-19 pandemic, but these early results hold promise,” Oxford researcher Sarah Gilbert said.
Write to Stu Woo at Stu.Woo@wsj.com and Peter Loftus at peter.loftus@wsj.com
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