After 'Unexplained Illness,' Big Vaccine Trial Pauses

AstraZeneca's coronavirus vaccine trial is on hold after a participant in a UK study developed what the pharmaceutical company calls "a potentially unexplained illness." The clinical trials of the experimental vaccine have been paused while safety data is reviewed and the illness is investigated, the Wall Street Journal reports. That means a US study that started last week, with a goal of enrolling 30,000 participants, will be temporarily halted. Studies are also underway in Latin America, Asia, Europe, and Africa.

The company says the move is a "routine action," and CNN reports it's meant to ensure the vaccine does not result in serious reactions among recipients. "In large trials, illnesses will happen by chance but must be independently reviewed to check this carefully," the company says in its statement. However, Stat News says the incident being investigated is "a suspected serious adverse reaction." Details have not been made public, but a source says the trial participant is expected to recover. The vaccine is one of three for COVID-19 that are in Phase 3, or late-stage, trials in the US. (More coronavirus stories.)