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Oxford University, AstraZeneca say their experimental vaccine is yielding promising results

LONDON — An Oxford University group and the British-Swedish pharmaceutical company AstraZeneca reported Monday that their coronavirus vaccine candidate, on which the US and European governments have placed substantial bets, was shown in early-stage human trials to be safe and to stimulate an immune response.

The study, published in the British medical journal the Lancet and involving 1,077 volunteers, was described as promising. A second report in the same medical journal on a Chinese vaccine showed what researchers not involved in the study call modest, positive results.

The two vaccines are among 23 candidates now being tested in human trials, according to a running tally kept by the World Health Organization. Over 130 others are in preclinical trials.

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Scientists caution that no one yet knows what level of immune response will be protective against the virus in the real world.

Last week, American researchers announced the first COVID-19 vaccine tested in the United States boosted people’s immune systems, and the shots will now enter the final phase of testing. That vaccine, developed by the National Institutes of Health and Cambridge, Mass.-based Moderna, produced the molecules key to blocking infection in volunteers who got it, at levels comparable to those in people who had survived a COVID-19 infection.

Moderna’s stock fell 12.83 percent Monday following news about Oxford’s vaccine candidate.

Much about the virus remains unknown. Last week, British researchers said people infected with it may see antibodies against it fade within months.

Still, researchers are optimistic they can stimulate a permanent guard against infection.

Large-scale, real-world trials of the Oxford vaccine are underway in Britain, Brazil, and South Africa. The United States plans to test it later this summer, along with a handful of other candidates, in clinical trials with about 30,000 volunteers each.

The Oxford vaccine is named ChAdOx1 nCoV-19 and was made from a weakened and nonreplicating version of a common cold virus, an adenovirus.

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Paul Offit, head of the Vaccine Education Center at Children’s Hospital of Philadelphia, said it’s unclear how protective the immune memory in T cells will be against coronavirus, in part because immune memory is typically more valuable against pathogens that have a longer incubation period than the coronavirus. his biggest concern about the Oxford study was that while the vaccine triggered the immune system best when given with a second shot, that two-dose regimen was tested in only 10 patients.

‘‘I’d want to see in a phase two trial: two doses consistently inducing a neutralizing antibody response — and that it’s relatively long lived, not months, not a few weeks,’’ Offit said.


Material from the Associated Press was used in this report.