AstraZeneca pauses COVID-19 vaccine trial after illness in a U.K. subject

AstraZeneca halted large, late-stage global trials of its coronavirus vaccine on Tuesday because of a serious suspected adverse reaction in a participant, the company said. It is not yet known whether the reaction was directly caused by the company's vaccine or was coincidental.

AstraZeneca halted large, late-stage global trials of its coronavirus vaccine on Tuesday because of a serious suspected adverse reaction in a participant, the company said. It is not yet known whether the reaction was directly caused by the company's vaccine or was coincidental. The pause will allow AstraZeneca to conduct a safety review and investigate whether the vaccine caused the illness. How long the hold will last is unclear. The halt is a setback for the vaccine effort, which has long been touted as one of the world's most advanced candidates. The shot had quickly progressed to late-stage studies in various countries, with AstraZeneca already signing contracts that could result in the delivery of initial doses this fall. The pause affects a study that began last week in the United States aiming to enroll 30,000 people, with funding from federal agencies. The study is testing whether the vaccine reduces the rate of COVID-19 cases compared with unvaccinated study subjects. AstraZeneca has promised to provide more than two billion doses of its experimental vaccine and has struck deals to sell the shot to various countries including the United States and United Kingdom. The British company is also working with partners to provide doses for low and middle-income countries.