 The study reports the results of an enhanced passive safety surveillance for three influenza vaccines, IIV3, IIV3, ID, and IIV4, during the 2017-18 influenza season in the UK and Republic of Ireland. The primary objective was to determine the rates of adverse reactions occurring within seven days following routine vaccination. At least one adverse reaction was reported by 2.9% of participants vaccinated with IIV3, ID, 1.4% of those vaccinated with IIV3, and 2.1% of those vaccinated with IIV4. The most frequent adverse reactions were injection site reactions and headache. No change was found compared to the known or expected adverse reaction rates for these vaccines during the 2017-18 season. This article was authored by Sonya Gandhubanga, and Lord Chappanen, Cecil Amin, and others.