A newly launched phase III trial of AZD-1222, an experimental coronavirus vaccine developed by Astrazeneca plc and Oxford University, has already been paused, the company said.

The unexpected news landed shortly after Astrazeneca CEO Pascal Soriot signed on to an industry pledge to "always make the safety and well-being of vaccinated individuals our top priority," now supported by the executives of nine industry leaders in COVID-19 vaccines development.

Holds are called for "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 provided to BioWorld.

It was unclear how serious the illness under investigation is or was and what impact the development will have on the trial's timeline. Nor was it immediately clear whether the FDA or Astrazeneca had initiated the pause in the trial. However, with an independent review underway to investigate the incident and substantial interest in the large-scale trial, further details are likely to emerge soon.

The first patient in the study, which is ultimately expected to enroll about 30,000 healthy adults, was dosed on August 28 at the JEM Research Institute clinical trial site in Lake Worth, Fla.

In late July, Astrazeneca posted interim data from AZD-1222’s phase I/II blinded, multicenter, randomized, controlled clinical trial of 1,077 healthy adults showing the vaccine was tolerated and generated a robust immune response against the virus. The data showed a fourfold increase in antibodies to the virus spike protein in 95% of the patients a month after injection. A T-cell response, peaking by day 14, was also induced and maintained for two months afterward.

Albany Molecular Research Inc. (AMRI), of Albany, N.Y., recently signed a supply agreement with Astrazeneca to support the manufacture of the adenovirus vector-based candidate. AMRI will be responsible for the sterile fill and finish at its drug product manufacturing facility in Albuquerque, N.M. The facility’s cGMP manufacturing capacity could potentially produce millions of doses of AZD-1222 annually, AMRI said.

The Serum Institute of India Pvt. Co. Ltd., the world’s largest vaccine manufacturer in volume terms, is also preparing to manufacture the vaccine. It has entered a $150 million agreement with Gavi, the Vaccine Alliance, and the Bill & Melinda Gates Foundation to initially produce up to 100 million doses of the Jenner Institute-developed “Oxford vaccine,” formerly ChAdOx1-nCov-19 vaccine. Oxford Biomedica plc, of Oxford, U.K., has signed a supply agreement with Astrazeneca for the vaccine too.