ABSTRACTPurposeThe European Medicines Agency (EMA) issued regulatory actions and communications in 2021 on thrombosis with thrombocytopenia syndrome (TTS) associated with adenovirus vector vaccines Vaxzevria or Jcovden. This study aimed to evaluate the impact of these actions on awareness, knowledge and implementation in practises of healthcare professionals (HCP).MethodsWeb‐based cross‐sectional surveys were conducted on HCPs engaged in the vaccination, monitoring or counselling about the vaccines. We measured awareness and knowledge of the risk of TTS and their implementation of recommendations in practise. Descriptive and qualitative analyses were conducted. This study took place in Greece, Latvia, Netherlands, Portugal and Slovenia.ResultsWe surveyed 1659 HCPs. From these, 914 were included in the analysis. Most were aware about the reports of TTS associated with COVID‐19 adenovirus vector vaccines, with countries reporting percentages between 85% and 97%. Mainstream media, health authorities and peers were the main sources of TTS risk information. Most HCPs were able to identify key symptoms from TTS but were less familiar with minor symptoms. Guidelines from health authorities on COVID‐19 vaccination impacted on professional practise of 55%–77% of HCPs. The reported use of product information across countries was moderate, with some variations.ConclusionsAwareness about and knowledge of TTS risk from COVID‐19 adenoviral vector vaccines were high among HCPs. HCPs reported a clear preference for national guidelines as source of risk information and the implementation of product information remained moderate across countries.