Screen grab taken from video issued by Britain's Oxford University, showing microbiologist Elisa Granato, being injected as part of the first human trials in the UK for a potential coronavirus vaccine, untaken by Oxford University, England, Thursday April 23, 2020. The first vaccine trial for COVID-19 Coronavirus have begun Thursday. (Oxford University Pool via AP)

Screen grab taken from video issued by Britain's Oxford University, showing microbiologist Elisa Granato, being injected as part of the first human trials in the UK for a potential coronavirus vaccine, untaken by Oxford University, England, Thursday April 23, 2020. The first vaccine trial for COVID-19 Coronavirus have begun Thursday. (Oxford University Pool via AP)

Testing of an experimental COVID-19 vaccine began in healthy volunteers in Britain Thursday, the latest in a cluster of early-stage studies in search of protection against the coronavirus.

University of Oxford researchers gave injections to volunteers in a study that eventually aims to include hundreds in hopes of telling not only if the vaccine is safe but if it works.

Researchers created the new vaccine by inserting genes for a spikey protein that studs the outer surface of the new coronavirus into another, harmless virus.

The idea: The immune system will spot the foreign protein and make antibodies to fight it, primed to react quickly if the person eventually is exposed to COVID-19.

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These kinds of studies often give volunteers either the real vaccine or a dummy shot. But this experimental vaccine may briefly cause soreness and maybe a low fever — meaning if a dummy shot was the comparison, the participants might figure out who got the real thing, said Dr. Andrew Pollard, one of the Oxford chief researchers.

“That might influence people’s behavior, perhaps make them more likely to be exposed to the virus,” which in turn would make it harder to prove if the vaccine worked, Pollard told The Associated Press.

So the Oxford team decided half the volunteers will be given an old vaccine against another disease that offers no COVID-19 protection but has similar shot side effects.

“It seems like the right thing to do — to ensure that we can combat this disease and get over it a lot faster,” volunteer Edward O’Neill told the BBC afterward.

Dozens of vaccine candidates are in various stages of development around the world. Experts have cautioned that even if early studies go well, it will be at least a year before any are available for widespread use.

Among those making the fastest progress: China’s CanSino Biologics has begun the second phase of testing its vaccine candidate, made with an approach similar to Oxford’s.

Two U.S. companies are testing vaccines made from copies of a piece of the virus’s genetic code. Two other Chinese candidates are being pursued that use older technology.

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The Associated Press receives support for health and science coverage from the Howard Hughes Medical Institute’s Department of Science Education. The AP is solely responsible for all content.