Well, that doesn’t sound good.

Courtesy of Stat News

A large, Phase 3 study testing a Covid-19 vaccine being developed by AstraZeneca and the University of Oxford at dozens of sites across the U.S. has been put on hold due to a suspected serious adverse reaction in a participant in the United Kingdom.

A spokesperson for AstraZeneca, a frontrunner in the race for a Covid-19 vaccine, said in a statement that the company’s “standard review process triggered a pause to vaccination to allow review of safety data.”

In a follow-up statement, AstraZeneca said it initiated the study hold. The nature of the adverse reaction and when it happened were not immediately known, though the participant is expected to recover, according to an individual familiar with the matter.

The spokesperson described the pause 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.” The spokesperson also said that the company is “working to expedite the review of the single event to minimize any potential impact on the trial timeline.”

An individual familiar with the development said researchers had been told the hold was placed on the trial out of “an abundance of caution.” A second individual familiar with the matter, who also spoke on condition of anonymity, said the finding is having an impact on other AstraZeneca vaccine trials underway — as well as on the clinical trials being conducted by other vaccine manufacturers.

To be fair, this is exactly why these trials are performed in the first place, to discover any adverse side effects, determine their cause, and then alter the vaccine formula accordingly. 

However, this is a huge trial on a vaccine that many folks had pinned their hopes on, so this pause is very concerning news.

I also illustrate quite effectively that we have a long way to go before we will see a safe effective vaccine ready for distribution to the public.