The shutdown of a global trial for a vaccine close to crossing the finish line proves the system is working as it should, local physicians say.

AstraZeneca, one of nine companies in the final phases of human trials for a COVID-19 vaccine, stopped the research Tuesday when a woman who received the vaccine – not a placebo – experienced neurological symptoms associated with a serious spinal inflammatory condition called transverse myelitis.

The drug maker’s chief executive, Pascal Soriot, reported the findings in a private conference call with investors that was reported on Wednesday morning.

He said the patient’s condition was improving although he did not confirm a diagnosis. He also said that AstraZeneca’s trial had been halted in July after another participant experienced neurological symptoms. That participant was later diagnosed with multiple sclerosis, which independent reviewers said had nothing to do with the trial.

“What I think you really are hearing is the sound of the system working,” said Dr. Stephen Threlkeld, infectious disease physician caring for COVID-19 patients at Baptist Memorial Hospital-Memphis.

“Everybody is nervous about the sort of upgraded timeline of approval. And it’s a tremendously charged – social and political – situation.

“You have people on one side accusing the other side of speeding this up for political expediency, despite the fact that it might not be safe. And you have the other side accusing the former side of slowing it down for political expediency,” Threlkeld said.

He described the situation as “depressing, really,” saying it will be critical to maintain scientific integrity in the process that ensues.

No one is predicting how long it could take to determine if the vaccine caused the reaction or if it was unrelated to the condition.

The analysis will be done by safety regulatory boards, independent of the federal government.

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“You always have an external, unbiased, unmotivated data-monitoring board that’s going to be invoked anytime there’s a set of, or any single adverse event,” said Paul Thomas, longtime influenza researcher at St. Jude Children’s Research Hospital who now is studying immunity in hospital employees who have had COVID-19.

Trials, he said, can and have been stopped for things that “seem almost absurd to the public.”

The classic example, he says, is of a trial that was stopped when a participant was the driver in a car accident.

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It’s possible that a medical event, triggered by something administered in the study, could have caused the accident.

“A lot of times protocols are written very broadly to say, ‘Well, we want you to be very safe and very, very sure there’s no unexpected, severe side effects to this experimental therapy that we’re developing,’ ” Thomas said.

The trial, he said, must stop, to make sure the accident was caused by the driver “changing the radio station or something else.”

In the AstraZeneca case, the reported condition, transverse myelitis, is “a bit more immunologically related,” which means a line could be drawn to the vaccine.

“This independent body needs to now collect the data, collect more clinical information from this particular patient and try to understand whether or not this is something that is of concern,” Thomas said.

He has seen investigations where it has taken months to a year to sort through the evidence and draw a final conclusion.

“In this case, there’s a ton of pressure to keep this moving forward but there’s also a ton of pressure to not do anything that looks like they’re rushing things,” he said.

AstraZeneca issued a statement Wednesday, saying it would be guided by an independent committee that would determine when to lift the hold “so that we can continue our work at the earliest opportunity to provide this vaccine broadly, equitably and at no profit during this pandemic.”

Eight other companies are also in the third round of human trials for COVID-19 vaccines.

At the third level, the trials typically involve tens of thousands of people across the world.

Last week, the Centers for Disease Control and Prevention told health departments in all 50 states to start laying the groundwork for how they will distribute COVID-19 vaccines expected to arrive in late October or early November, presumably before the presidential election on Nov. 3.

The Shelby County Health Department is planning a mass influenza vaccination program on Nov. 19, which it will use to gather information on how the COVID-19 vaccine rollout should go.

Dr. Anthony Fauci, head of the National Institute of Allergy and Infectious Diseases, on Wednesday said he was sticking to his projection that a safe and effective vaccine will be available by the end of the year.

“Likely November, December. Is it possible, is it conceivable that we could find out earlier? Say October? Certainly, that’s possible,” Fauci said. “I think it’s unlikely, but you can’t rule it out. I think the more likely scenario is that we will know by the end of this calendar year, and hopefully we’ll be able to start vaccinations in earnest as we begin 2021.”