Dear Editor,We read the response by Mungmunpuntipantip and Wiwanitkit [1] on our article “Description of Frequencies of Reported Adverse Events Following Immunization Among Four Different COVID-19 Vaccine Brands” [2]. Because experienced common adverse events following immunization (AEFIs) were asked for in predefined questions to all participants in the cohort we do not assume there is a high chance of underreporting. It is correct that not all mentioned events will be adverse reactions. That is incorporated in the definition of an AEFI: adverse event following immunization is any untoward medical occurrence which follows immunization and which does not necessarily have a causal relationship [3]. An experienced AEFI can also be due to nocebo effect, or background incidence.Yours sincerely Agnes Kant and Florence van Hunsel (Corresponding Author)