JNJ Johnson and Johnson

By Jenny Strasburg and Drew Hinshaw 

The pause of Johnson & Johnson's Covid-19 vaccine trials poses another setback for global efforts to develop a shot to protect lives and jump-start economies battered by the pandemic, as well as a reminder of the challenges of fast-tracking vaccine development.

J&J said Monday it had paused all trials of its vaccine, including a large-scale Phase 3 trial it started last month in the U.S., after a study volunteer developed an unexplained illness. The halt comes a little more than a month after AstraZeneca PLC paused trials of a shot it is developing with the University of Oxford, citing similar reasons. AstraZeneca has since resumed trials in the U.K. but a large U.S. study remains on hold.

The dual setbacks affect two of four front-runner vaccine candidates being developed in the West. With winter approaching, world leaders hoped late-stage clinical trials could translate into approved vaccines that could be distributed to those most in need, including health care workers, and eventually to the broader population.

The prospect of a Covid-19 vaccine by year-end has been a feature of political campaigns in the U.S. and fueled hopes for the reopening of countries in Europe and elsewhere. That has been underscored recently by rising coronavirus infection rates that have led to new lockdowns and kept millions of workers and students at home.

U.S. stock futures ticked lower Tuesday as the J&J news prompted concern that it could take longer than expected for a vaccine to be widely available. J&J is scheduled to report quarterly earnings later Tuesday.

Though it is unclear how long the vaccine trials will be paused, the delays demonstrate how challenging vaccines are to develop. Typically vaccines take years to go from laboratory to distribution, but scientists are aiming for a far more ambitious time frame amid the pandemic.

Doctors and analysts are watching closely for signs of any negative side effects that could dim the promise of one or more vaccines, and in turn diminish the prospect of swaths of the global population developing what's known as herd immunity. The idea is that vaccinating large chunks of the population protects even those who can't or don't receive a vaccine by stopping the spread of a disease.

While health authorities stress that not enough is known about the vaccine trial pauses to draw conclusions, they also warn that the increased threat of side effects from a shot could lead to fewer people -- such as children or pregnant women -- being safely vaccinated. It could also reduce some people's willingness to receive a vaccine.

"This raises questions about the whole concept of herd immunity and whether it's achievable," said Dr. Justin Stebbing, a professor of oncology at Imperial College London. He said information known so far is insufficient to answer that question.

J&J's Covid-19 vaccine is one of the most advanced in development. Only a handful have entered the third and final stage of testing in the U.S., including candidates from AstraZeneca, Moderna Inc. and Pfizer Inc.

J&J said Monday that the study volunteer's illness was now being reviewed by an independent data-safety monitoring board. The board needs to assess whether the subject's illness was related to the vaccine or not, a person familiar with the matter said.

The company didn't disclose more information about the illness but said its trial guidelines "ensure our studies may be paused if an unexpected serious adverse event that might be related to a vaccine or study drug is reported, so there can be a careful review of all of the medical information before deciding whether to restart the study."

The World Health Organization said Tuesday that temporary suspensions of vaccine clinical trials aren't unusual and that it was pleased vaccine developers were ensuring the scientific integrity of trials and abiding by standard guidelines.

"Safety is the primary focus for vaccine clinical trials," the WHO said. "When a potentially unexplained illness occurs in a trial participant, which may or may not be related to the vaccine being evaluated, it is rigorous, routine practice to investigate."

Write to Jenny Strasburg at jenny.strasburg@wsj.com and Drew Hinshaw at drew.hinshaw@wsj.com

(END) Dow Jones Newswires

October 13, 2020 07:10 ET (11:10 GMT)

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