FILE PHOTO: Small bottles labeled with a "Vaccine COVID-19" sticker and a medical syringe are seen in this illustration Reuters AstraZeneca’s vaccine study is being investigated further by the Food & Drug Administration (FDA) after a participant experienced a suspected adverse reaction to the drug. This could put additional delays on the British drugmaker’s late-stage trial. Meanwhile, European regulators are set to announce the start of AstraZeneca’s review in Europe as soon as this week - the first vaccine to undergo EU approval. AstraZeneca’s CEO said on September 10 the vaccine would be ready by the end of the year or early next year, despite the COVID-19 trial halting due to the illness. Visit Business Insider's homepage for more stories. The US Food and Drug Administration (FDA) has broadened its investigation into the suspected adverse reaction of a participant in AstraZeneca's COVID-19 vaccine trial, whilst European regulators are set to announce its review as soon as this week.The FDA also wants to examine results from earlier studies of other vaccines produced by the same scientists of the AstraZeneca vaccine to see if similar side effects have emerged, three sources with knowledge of the trial told Reuters on Wednesday.