FILE - In this Aug. 14, 2020, file photo, laboratory technicians work at the mAbxience biopharmaceutical company on an experimental coronavirus vaccine developed by Oxford University and the laboratory AstraZeneca in Garin, Argentina. AstraZeneca announced Monday, Aug. 31, its vaccine candidate has entered the final testing stage in the U.S. (AP Photo/Natacha Pisarenko, File)

FILE - In this Aug. 14, 2020, file photo, laboratory technicians work at the mAbxience biopharmaceutical company on an experimental coronavirus vaccine developed by Oxford University and the laboratory AstraZeneca in Garin, Argentina. AstraZeneca announced Monday, Aug. 31, its vaccine candidate has entered the final testing stage in the U.S. (AP Photo/Natacha Pisarenko, File)

AstraZeneca COVID-19 vaccine study paused after one illness

An AstraZeneca spokesperson confirmed the pause in vaccinations covers studies in the U.S. and other countries

Late-stage studies of AstraZeneca’s COVID-19 vaccine candidate are on temporary hold while the company investigates whether a recipient’s “potentially unexplained” illness is a side effect of the shot.

In a statement issued Tuesday evening, the company said its “standard review process triggered a pause to vaccination to allow review of safety data.”

AstraZeneca didn’t reveal any information about the possible side effect except to call it “a potentially unexplained illness.” The health news site STAT first reported the pause in testing, saying the possible side effect occurred in the United Kingdom.

An AstraZeneca spokesperson confirmed the pause in vaccinations covers studies in the U.S. and other countries. Late last month, AstraZeneca began recruiting 30,000 people in the U.S. for its largest study of the vaccine. It also is testing the vaccine, developed by Oxford University, in thousands of people in Britain, and in smaller studies in Brazil and South Africa.

Two other vaccines are in huge, final-stage tests in the United States, one made by Moderna Inc. and the other by Pfizer and Germany’s BioNTech. Those two vaccines work differently than AstraZeneca’s, and the studies already have recruited about two-thirds of the needed volunteers.

Temporary holds of large medical studies aren’t unusual, and investigating any serious or unexpected reaction is a mandatory part of safety testing. AstraZeneca pointed out that it’s possible the problem could be a coincidence; illnesses of all sorts could arise in studies of thousands of people.

“We are working to expedite the review of the single event to minimize any potential impact on the trial timeline,” the company statement said.

It’s likely the unexplained illness was serious enough to require hospitalization and not a mild side effect such as fever or muscle pain, said Deborah Fuller, a University of Washington researcher who is working on a different COVID-19 vaccine that has not yet started human testing.

“This is not something to be alarmed about,” Fuller said. Instead, it’s reassuring that the company is pausing the study to figure out what’s happening and carefully monitoring the health of study participants.

Dr. Ashish Jha of Brown University said via Twitter that the significance of the interruption was unclear but that he was “still optimistic” that an effective vaccine will be found in the coming months.

“But optimism isn’t evidence,” he wrote. “Let’s let science drive this process.”

Angela Rasmussen, a virologist at Columbia University in New York, tweeted that the illness may be unrelated to the vaccine, “but the important part is that this is why we do trials before rolling out a vaccine to the general public.”

During the third and final stage of testing, researchers look for any signs of possible side effects that may have gone undetected in earlier patient research. Because of their large size, the studies are considered the most important study phase for picking up less common side effects and establishing safety.

The trials also assess effectiveness by tracking who gets sick and who doesn’t between patients getting the vaccine and those receiving a dummy shot.

The development came the same day that AstraZeneca and eight other drugmakers issued an unusual pledge, vowing to uphold the highest ethical and scientific standards in developing their vaccines.

The announcement follows worries that President Donald Trump will pressure the U.S. Food and Drug Administration to approve a vaccine before it’s proven to be safe and effective.

The U.S. has invested billions of dollars in efforts to quickly develop multiple vaccines against COVID-19. But public fears that a vaccine is unsafe or ineffective could be disastrous, derailing the effort to vaccinate millions of Americans.

Representatives for the FDA did not immediately respond to requests for comment Tuesday evening.

AstraZeneca’s U.S.-traded shares fell more than 6% in after-hours trading following reports of the trial being paused.

___

Associated Press writers Matthew Perrone and Carla K. Johnson contributed to this report.

___

The Associated Press Health and Science Department receives support from the Howard Hughes Medical Institute’s Department of Science Education. The AP is solely responsible for all content.

Lauran Neergaard, The Associated Press

Coronavirusvaccines

Get local stories you won't find anywhere else right to your inbox.
Sign up here

Just Posted

The Thornhill Volunteer Fire Department responded to an engine Dec. 3 on Highway 16, using a compressed air and foam solution to extinguish the flames. (Submitted Photo/Krista Bowman)
Semi truck engine catches fire in Thornhill

Firefighters used a compressed air and foam solution to put out the fire

A volunteer committee is urging the provincial government to complete grizzly habitat mapping. (Ivan Hardwick photo)
Volunteer committee urges province to complete grizzly habitat mapping

Committee says only 18 of 37 watersheds have been mapped, province has spent $500,000 so far

A coal-fired power plant seen through dense smog from the window of an electric bullet train south of Beijing, December 2016. China has continued to increase thermal coal production and power generation, adding to greenhouse gas emissions that are already the world’s largest. (Tom Fletcher/Black Press)
LNG featured at B.C. energy industry, climate change conference

Hydrogen, nuclear, carbon capture needed for Canada’s net-zero goal

Terrace RCMP arrested an impaired driver and found illicit drugs, weapons and stolen property in the vehicle on Nov. 28, 2020. (File Photo)
Terrace RCMP arrest impaired driver in possession of weapons

Weapons, illicit drugs, stolen property found in vehicle

A COVID-19 exposure has been recorded at Centennial Christian School in Terrace. The exposure occurred between Nov. 23 and Nov. 26, 2020. (Centennial Christian School Facebook photo)
COVID-19 exposure recorded at Centennial Christian School in Terrace

It’s the first known school exposure in Terrace

Motorists wait to enter a Fraser Health COVID-19 testing facility, in Surrey, B.C., on Monday, Nov. 9, 2020. THE CANADIAN PRESS/Darryl Dyck
Another 694 diagnosed with COVID-19 in B.C. Thursday

Three more health care outbreaks, 12 deaths

A demonstrator wears representations of sea lice outside the Fisheries and Oceans Canada offices in downtown Vancouver Sept. 24, demanding more action on the Cohen Commission recommendations to protect wild Fraser River sockeye. (Quinn Bender photo)
First Nations renew call to revoke salmon farm licences

Leadership council implores use of precautionary principle in Discovery Islands

Ten-month-old Aidan Deschamps poses for a photo with his parents Amanda Sully and Adam Deschamps in this undated handout photo. Ten-month-old Aidan Deschamps was the first baby in Canada to be diagnosed with spinal muscular atrophy through Ontario’s newborn screening program. The test was added to the program six days before he was born. THE CANADIAN PRESS/HO, Children’s Hospital Eastern Ontario *MANDATORY CREDIT*
First newborn tested for spinal muscular atrophy in Canada hits new milestones

‘If Aidan had been born any earlier or anywhere else our story would be quite different’

(Pixabay)
Canadians’ mental health has deteriorated with the second wave, study finds

Increased substance use one of the ways people are coping

An RCMP officer confers with military rescuers outside their Cormorant helicopter near Bridesville, B.C. Tuesday, Dec. 1. Photo courtesy of RCMP Cpl. Jesse O’Donaghey
Good Samaritan helped Kootenay police nab, rescue suspect which drew armed forces response

Midway RCMP said a Good Samaritan helped track the suspect, then brought the arresting officer dry socks

People line up at a COVID-19 assessment centre during the COVID-19 pandemic in Scarborough, Ont., on Wednesday, December 2, 2020. Toronto and Peel region continue to be in lockdown. THE CANADIAN PRESS/Nathan Denette
COVID-19 vaccine approval could be days away as pressures mount on health-care system

Many health officials in regions across the country have reported increasing pressures on hospitals

(Needpix.com)
Pandemic has ‘exacerbated’ concerns for B.C. children and youth with special needs: report

Pandemic worsened an already patchwork system, representative says

Most Read