A late-stage clinical trial of a promising coronavirus vaccine has been put on hold after a study participant experienced a severe adverse event. Investigators are working to determine whether the case of spinal inflammation was caused by the vaccine and what that would mean for this and other trials going forward.
A woman in the United Kingdom who volunteered for a trial of a COVID-19 vaccine from AstraZenaca and the University of Oxford developed what appears to be transverse myelitis, a serious condition involving inflammation of the spinal cord. The condition has been linked to viral infections and, in rare cases, to vaccines for other diseases, and it is also associated with autoimmune conditions such as multiple sclerosis and lupus.
AstraZeneca CEO Pascal Soriot told investors that the woman was randomly assigned to receive the active vaccine rather than a placebo, STAT News reported. He added that she is improving and is expected to be released from the hospital soon. Soriot also confirmed that the trial was previously halted in July after a participant developed neurological symptoms that were later diagnosed as multiple sclerosis and deemed unrelated to the vaccine.
AstraZeneca has paused vaccination across all trials to allow an independent committee to review the safety data related to the event. Adverse events are not unusual in clinical trials of experimental vaccines and treatments, and it is standard procedure to halt a study temporarily while the event is investigated.
“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. “AstraZeneca is working to expedite the review of the single event to minimize any potential impact on the trial timeline. We are committed to the safety of our participants and the highest standards of conduct in our trials.”
The AstraZeneca vaccine, dubbed AZD1222, uses a weakened chimpanzee adenovirus—similar to viruses that cause the common cold—as a vector to deliver genes encoding the spike protein from the coronavirus, officially named SARS-CoV-2.
This is one of several COVID-19 vaccines that have shown promise in early studies and are now in large Phase III trials, the final step of human testing. A vaccine candidate being developed by CanSino Biologics in China uses a human adenovirus vector, as does a Russian vaccine that is already in use while late-stage trials are underway. Vaccine candidates being developed by Moderna and Pfizer-BioNTech are based on messenger RNA from SARS-CoV-2, while three other Chinese vaccines use inactivated coronavirus.
Testifying before the Senate HELP Committee today at 10:00 am ET with @Surgeon_General Jerome Adams. We’ll discuss how vaccines protect public health & save lives, & how we ensure they are safe. @NIH to live tweet. Watch the hearing here: https://t.co/9zQt6c57Am #COVID19 #NIH
— Francis S. Collins (@NIHDirector) September 9, 2020
The trial pause comes amid concern that COVID-19 vaccines could be approved prematurely. President Donald Trump has raised the prospect that the Food and Drug Administration could issue an emergency use authorization before the election on November 3, leading to fears that one or more vaccines could get the green light before there is adequate evidence confirming their safety and effectiveness. A recent Kaiser Family Foundation poll found that 62% of Americans are worried that a vaccine could be hastily authorized due to political pressure.
National Institutes of Health director Francis Collins, MD, PhD, and Surgeon General Jerome Adams, MD, MPH, sought to allay such concerns during a September 9 hearing before the Senate Health, Education, Labor and Pensions Committee.
According to Collins, the AstraZenaca trial pause shows that the process is working as it should.
“The announcement yesterday about the AstraZeneca vaccine is a concrete example of how even a single case of an unexpected illness is sufficient to require a clinical hold for the trial in multiple counties,” he said.
Collins added that if an investigation determines that the vaccine caused the adverse event, it would be eliminated from consideration and existing doses would be thrown out.
“The reason we’re investing not in one, but in six different vaccines is because of the expectation that they won’t all work,” he said.
Drug companies developing COVID-19 vaccines also sought to put such fears to rest, with nine CEOs issuing an unprecedented pledge that they would not seek approval or emergency authorization for a vaccine until its safety and effectiveness has been confirmed in trials.