Please ensure Javascript is enabled for purposes of website accessibility

AstraZeneca Coronavirus Vaccine Clinical Trial Paused

By Brian Orelli, PhD – Sep 8, 2020 at 6:28PM

You’re reading a free article with opinions that may differ from The Motley Fool’s Premium Investing Services. Become a Motley Fool member today to get instant access to our top analyst recommendations, in-depth research, investing resources, and more. Learn More

One participant fell ill, but the connection to treatment with AZD122 is unclear.

According to an article in Stat, AstraZeneca (AZN -3.07%) has paused the U.S. clinical trial of its coronavirus vaccine, AZD1222, after a serious possible adverse event arose in a patient enrolled in a clinical trial testing AZD122 in the U.K.

At this point, the nature of the adverse event is not known, and it isn't clear whether it was caused by AZD122. The company is "working to expedite the review of the single event to minimize any potential impact on the trial timeline," according to Stat. The participant is expected to recover. 

In addition to the 30,000-participant U.S. study announced last week, AstraZeneca is also running clinical trials in the U.K., Brazil, and South Africa. The company plans to start studies in Japan and Russia as well. All told, the studies will enroll up to 50,000 participants globally.

Care provider giving a shot into an arm.

Image source: Getty Images.

It isn't publicly known exactly how many patients have received AZD1222, but investors can get some clues from Moderna (MRNA -0.55%), which had enrolled 21,411 participants in its late-stage coronavirus vaccine clinical trial as of Friday. Meanwhile, vaccine collaborators Pfizer (PFE -1.10%) and BioNTech (BNTX -1.27%) had enrolled 25,189 participants as of an update on Monday.

With that many people enrolled in coronavirus clinical trials, it's highly likely that one of the participants would develop a serious illness unrelated to the vaccination. Of course, proving that it's unrelated could be challenging and might only be possible by testing AZD122 on more participants. If the adverse event only occurs in one out of 50,000 participants, it's either unrelated or a side effect with such a low incidence level that it's a tolerable issue.

Shares of AstraZeneca were down 6.5% at 6:40 p.m. EDT in after-hours trading.

Brian Orelli, PhD has no position in any of the stocks mentioned. The Motley Fool has no position in any of the stocks mentioned. The Motley Fool has a disclosure policy.

Invest Smarter with The Motley Fool

Join Over 1 Million Premium Members Receiving…

  • New Stock Picks Each Month
  • Detailed Analysis of Companies
  • Model Portfolios
  • Live Streaming During Market Hours
  • And Much More
Get Started Now

Stocks Mentioned

AstraZeneca PLC Stock Quote
AstraZeneca PLC
$54.58 (-3.07%) $-1.73
Pfizer Inc. Stock Quote
Pfizer Inc.
$44.08 (-1.10%) $0.49
Moderna, Inc. Stock Quote
Moderna, Inc.
$123.64 (-0.55%) $0.68
BioNTech SE Stock Quote
BioNTech SE
$128.35 (-1.27%) $-1.65

*Average returns of all recommendations since inception. Cost basis and return based on previous market day close.

Related Articles

Motley Fool Returns

Motley Fool Stock Advisor

Market-beating stocks from our award-winning analyst team.

Stock Advisor Returns
S&P 500 Returns

Calculated by average return of all stock recommendations since inception of the Stock Advisor service in February of 2002. Returns as of 09/25/2022.

Discounted offers are only available to new members. Stock Advisor list price is $199 per year.

Premium Investing Services

Invest better with The Motley Fool. Get stock recommendations, portfolio guidance, and more from The Motley Fool's premium services.