Talk to Patients About: Vaccine Testing
By Sean Price Texas Medicine November 2020

The COVID-19 vaccines currently under production are expected to reach the public faster than any previous vaccine. (See “Our Best Shot,” pages 16-21.) But no matter how quickly a vaccine is produced, it still must pass a series of rigorous scientific tests before the U.S. Food and Drug Administration (FDA) will license it for public use.

The timeline has been condensed mainly in bureaucratic aspects of vaccine making, such as getting FDA approvals, says Charles Andrews, MD. He is director of clinical research at Diagnostics Research Group in San Antonio, which does clinical testing for vaccines and medicines. Also, the health emergency has freed up more money for vaccine developers to hire more staff and accelerate time-consuming steps, like processing patient data.

However, safety testing remains the same, Dr. Andrews emphasizes.

Assuming that laboratory and animal testing goes well, the vaccine maker moves to testing on people (

With FDA approval, the vaccine maker can start clinical trials, which take place in three phases. Small groups of people receive the shot in Phase I and Phase II; tens of thousands of people receive it in Phase III in randomized, double-blind tests in which the proposed vaccine is tested against a placebo. The vaccine maker and FDA monitor each phase and can halt it at any time for safety concerns. 

“You get real good signals about safety from Phase I and Phase II,” Dr. Andrews said. “And they’re still looking at safety in Phase III. But the efficacy, whether it really works, that’s a Phase III [question].”

Data from the Phase III tests goes to FDA for review. If the vaccine is licensed, FDA continues to monitor its progress and may require further testing, Dr. Andrews says.

But getting a vaccine license from the FDA is hardly a sure thing, he cautions. Some vaccine developers spend hundreds of millions of dollars just to have FDA turn them down.

“It’s usually for lack of efficacy that they don’t get approved,” Dr. Andrews said.


Tex Med. 2020;116(11):23
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Last Updated On

October 30, 2020

Originally Published On

October 30, 2020

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