A participant got inflammatory syndrome resulting the pharmaceutical company AstraZeneca halting global trials of its coronavirus vaccine on Tuesday.
Speaking on the condition of anonymity, a person familiar with the situation, said that the individual-a volunteer in the UK trial had been found to have transverse myelitis, an inflammatory syndrome that affects the spinal cord and is often sparked by viral infections, reports New York times.
The participant had been enrolled in a Phase 2/3 trial based in the United Kingdom. However, the timing of this diagnosis, and whether it was directly linked to AstraZeneca's vaccine, is unclear.
The trial's halt, which was first reported by Stat News, will allow the British-Swedish company to conduct a safety review. How long the hold will last is unclear.
In a statement, the company described the halt as 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."
In large trials like the ones AstraZeneca is overseeing, the company said, participants do sometimes become sick by chance, but such illnesses "must be independently reviewed to check this carefully."
The company said it was "working to expedite the review of the single event to minimize any potential impact on the trial timeline" and that it was "committed to the safety of our participants and the highest standards of conduct in our trials."
AstraZeneca's vaccine, known as AZD1222, relies on a chimpanzee adenovirus that has been modified to carry coronavirus genes and deliver them into human cells. Although the adenovirus is generally thought to be harmless, the coronavirus components of the vaccine are intended to incite a protective immune response that would be roused again should the actual coronavirus try to infect a vaccinated individual.
Adenoviruses, however, can sometimes trigger their own immune responses, which could harm the patient without generating the intended form of protection.
AstraZeneca's vaccine is currently in Phase 2/3 trials in England and India, and in Phase 3 trials in Brazil, South Africa and more than 60 sites in the United States. The company intended for its US enrollment to reach 30,000.
AstraZeneca is one of three companies whose vaccines are in late-stage clinical trials in the United States.