Johnson & Johnson vaccine trial suspended before starting in Bay Area; here's what happens next

SAN FRANCISCO (KGO) -- Researchers at Stanford were just days away from joining a trial of an extremely promising COVID-19 vaccine candidate. Then came word that manufacturer Johnson & Johnson is pausing the study, after a participant became sick with what's described as an unexplained illness. Now, comes the challenge of figuring out why.

"They'll need to do follow up, lab tests, clinical exams, maybe even radiologic testing, we just don't know what the issue is," says Dr. Yvonne Maldonado, M.D.

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Dr. Maldonado is an infectious disease expert at Stanford. Although she was not directing the Johnson & Johnson trial, she says the interruption isn't unusual.

"This happens all the time. I wouldn't put a lot of stock in it, yet. Now, of course, it could be a big safety signal, but we just don't know. Every trial, virtually every trial will have an adverse event," argues Dr. Maldonado.

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That's in part, because researchers cast just a wide net, recruiting thousands of participants to increase the odds they'll catch any rare side effects. And since the trials are blind, Johnson & Johnson may not even know yet whether the patient received its vaccine or a placebo.

The vaccine was widely anticipated, because the company recently used a similar technique to create a successful Ebola vaccine in Africa. It also a single dose injection, does not need to be refrigerated and is easily transportable.

"But again, this is why we have so many vaccine candidates, because we just don't know which one will work. And it's very hard to predict any side effects," she believes.

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Case in point, another vaccine candidate from AstraZeneca. It was scheduled to enter trials at UCSF and other sites, when the study was halted last month because of an illness. That trial was restarted in England, but is now facing concerns again, after a second patient reportedly suffered neurological problems. It is currently still on hold in the U.S.

As for Stanford, they say they have several other potential vaccine trials in the pipeline, with companies including Pfizer and Novavax.

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