A group you've probably never heard of holds powerful sway over which coronavirus vaccines will end up on the market.

It's known as the DSMB.
Members of a Data and Safety Monitoring Board are the only ones who get to look under the hood while a trial is ongoing. They know who has been given a Covid-19 vaccine, and who has gotten a placebo. The very doctors running the trials, the pharmaceutical companies that developed the vaccines, and even the US Food and Drug Administration don't know.
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Armed with that secret, only the DSMB can monitor how safe and effective a vaccine is shaping up to be.
One word from the DSMB, and a trial can be stopped. That's what happened to the AstraZeneca trial in early September after a study participant developed neurological symptoms. Shortly after, it came to light that the same trial had been paused briefly in July for similar reasons. While the vaccine trial resumed in the UK, it is still on pause in the US.
"They're very powerful. They're key guardians of science and safety and are as important if not more important than the FDA," said bioethicist Art Caplan.
The need for anonymity
Earlier this year, the National Institutes of Health appointed a common DSMB to monitor Covid-19 vaccine clinical trials that are being funded by the federal government under Operation Warp Speed. This DSMB has 10 to 15 members with specialties including vaccine development, statistics and ethics.
It's not a glamorous or public-facing job. They're paid only a modest honorarium by the NIH -- just $200 per meeting -- and there are no press conferences, no TV interviews, no fame and no glory.
That's because members' names aren't typically revealed while trials are in progress to shield them from external pressures.
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Caplan, who has served on about 20 DSMBs, said there's a good reason members' names are kept secret.
"You wouldn't want some investor calling a DSMB member and saying 'Hey, how's this clinical trial looking? If you tell me, I'll give you 10% of whatever I make,'" said Caplan.
Carrie Wolinetz, associate director for science policy at the National Institutes of Health, said various types of people might try to influence DSMB members.
"It doesn't have to be nefarious. Parents of a very ill child might be anxious about how the trial of a drug that could help their child is going, and they might contact the folks at the DSMB. Keeping their names private is a way to preserve independence of the group," she said.
There's a lot at stake. They scrutinize the data carefully. One word from them, and a vaccine's chances of coming to market could be squashed. Millions of dollars spent on research and development could all be for naught.
While there are good arguments for secrecy, Caplan said he disagrees with the confidentiality that currently shrouds the DSMBs for Covid-19 vaccine candidates.
"We need to know if we can trust the vaccine, so the more transparency the better," Caplan said.
In order to reach population immunity through a vaccine, a large proportion of the US public needs to get vaccinated. But confidence in a potential vaccine is low -- 49% of Americans say they definitely or probably would not get a vaccine if one were available now, according to a recent poll by the Pew Research Center.
"We want to know they're fully independent, that they have no prior relationships with the company. So they're not conflicted in any way," said Dr. Eric Topol, professor of molecular medicine at Scripps Research. "We want to know about their expertise. It's important to know who they are."