ObjectiveIn 2012, Lao PDR introduced seasonal influenza vaccine in pregnant women, persons aged 50years, persons with chronic diseases, and healthcare personnel. We assessed adverse events following immunization (AEFI). MethodsWe used a multistage randomized cluster sample design to interview vaccine recipients. FindingsBetween April and May 2012, 355902 were vaccinated. Of 2089 persons interviewed, 261 (125%) reported one or more AEFI. The most commonly reported AEFIs were local reactions. No hospitalizations or deaths were reported; 16% sought medical care. Acceptance and awareness of vaccination were high. ConclusionsFollowing the introduction of seasonal influenza vaccine in Lao PDR, self-reported adverse events were mild.