Scientists see an upside to AstraZeneca halting its COVID-19 vaccine trial

September 9, 2020, 12:52 PM UTC

On Tuesday, the British vaccine maker AstraZeneca announced that it had temporarily halted its Phase III vaccine trials after one participant injected with the vaccine came down with a serious, unexplained illness.

AstraZeneca, which is developing the vaccine in partnership with Oxford University, said its “standard review process” triggered the pause “to allow review of safety data.”

“This is a routine action which has to happen whenever there is a potentially unexplained illness in one of the trials, while it is investigated, ensuring we maintain the integrity of the trials,” the company said in a statement.

Investors seemed to lose confidence in the company’s vaccine effort immediately.

Subscribe to The Capsule, a daily brief monitoring advances in health care and biopharma, delivered free to your inbox.

Shares of AstraZeneca fell by 6% in after-hours trading in London. In China, shares for BioKangtai, a Chinese pharmaceutical company that signed a licensing deal with AstraZeneca in August to distribute the vaccine in China, fell by nearly 20% in Wednesday trading in Shenzhen.

Scientists, however, have a different outlook. They say the trial pause shouldn’t diminish hope in AstraZeneca’s vaccine. In fact, they say AstraZeneca’s decision to halt the trial demonstrates that the vaccine maker is valuing science and public safety over speed, even as the race to develop a COVID-19 vaccine becomes politicized in the U.S., where President Donald Trump has repeatedly tied a vaccine’s approval to his reelection bid.

“I’m not alarmed,” Faheem Younus, chief of infectious diseases at the University of Maryland’s medical school, wrote on Twitter. “Side effects, stops and re-starts are part of a GOOD careful process.”

News that AstraZeneca paused its trials, which are taking place in the U.S., U.K., Brazil, and South Africa, came a day after the company signed a pledge with eight other major vaccine developers to commit to “high ethical standards” and “sound scientific principles” in their efforts to rapidly develop and produce a COVID-19 vaccine.

Halting the trials shows that AstraZeneca is “prioritizing science over politics,” says Nicholas Thomas, an expert in infectious diseases and health governance at the City University of Hong Kong. “Given the large size of any Phase III trial, it is not surprising that there would be some adverse reactions. But it is only by gathering the negative results that the final product can be made safer.”

Eugene Hung, molecular virologist at the Hong Kong University of Science and Technology, was more cautious, saying the scientific community and the broader public should reserve judgment until AstraZeneca discloses more about what caused the volunteer’s illness.

Stat broke the news about AstraZeneca’s trials on Tuesday night before the company issued its statement. It’s not clear whether the vaccine maker would have publicly announced the pause in the trials otherwise. The U.K. government requires vaccine makers to report “serious adverse reactions” in vaccine trials to government regulators within seven days of them occurring. Thomas says that vaccine makers usually publicly disclose such developments at the end of a trial.

He argues that the revelation now may ultimately increase public confidence in the company’s ongoing efforts.

This “bolsters [AstraZeneca’s] reputation in taking a more careful approach” in developing a vaccine, Thomas says.

He argues that the Stat scoop also underscores the importance of the press in serving as an additional check on the vaccine race, especially as inoculations are developed and tested in countries with little government transparency or accountability.

Scientists like Thomas see the AstraZeneca news as an ordinary part of trials, but the pause is the first major hiccup in what’s arguably the most-watched drug development process in history.

Until now, the leading COVID-19 vaccine makers—AstraZeneca, Moderna, Pfizer, Johnson & Johnson, CanSino, Sinovac—have sped their candidates through early-stage trials with encouraging results. In the meantime, the coronavirus has sickened 27.5 million worldwide and killed nearly 900,000. Second and third waves of the virus have underscored the limits of low-tech containment strategies like face masks and social distancing and bolstered the need for a vaccine.

The case for a COVID-19 vaccine is clear, yet public confidence in one remains delicate, especially in the worst-hit country, the U.S. In August, a Gallup poll found that 35% of Americans would not be willing to take a COVID-19 vaccine even if it was approved by the U.S. government and provided for free.

In halting its vaccine trials, AstraZeneca appeared to make the prudent decision, but health officials may have to persuade skeptical members of the public to see the delay as some scientists do—as a positive.

More must-read international coverage from Fortune:

Subscribe to Well Adjusted, our newsletter full of simple strategies to work smarter and live better, from the Fortune Well team. Sign up today.