"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.
RELATED: Here's how COVID-19 reinfection may impact immunity, vaccine development
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.
VIDEO: What will it take to get a COVID-19 vaccine and how will it be made?
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.
I-TEAM: Experts warn of possible problems distributing COVID-19 vaccine to California nursing homes
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.
App users: For a better experience, click here to view the full map in a new window
If you have a question or comment about the coronavirus pandemic, submit yours via the form below or here.
Get the latest news, information and videos about the novel coronavirus pandemic here
RELATED STORIES & VIDEOS:
- Map: CA counties that can, can't reopen under new rules
- Updated number of COVID-19 deaths, cases in Bay Area
- COVID-19 Help: Comprehensive list of resources, information
- California EDD: The most commonly asked questions we get about unemployment and PUA
- How to tell the difference between seasonal allergies and coronavirus symptoms
- Here's which mask is better to protect from COVID-19
- First COVID-19 vaccine volunteers in US describe experience as Bay Area launches vaccine trials
- From salons to dinner parties: Experts rate the risk of 12 activities
- Coronavirus origin: Where did COVID-19 come from?
- What is a COVID-19 genetic, antigen and antibody test?
- What will it take to get a COVID-19 vaccine and how will it be made?
- What does COVID-19 do to your body and why does it spread so easily?
- Here's how shelter in place, stay at home orders can slow spread of COVID-19
- Coronavirus Timeline: Tracking major moments of COVID-19 pandemic in San Francisco Bay Area
- COVID-19 Diaries: Personal stories of Bay Area residents during novel coronavirus pandemic
- Coronavirus Doctor's Note: Dr. Alok Patel gives his insight into COVID-19 pandemic