Perspectives on the impact of regulatory measures on national COVID-19 vaccination programs: a qualitative study from six EU member states

Background: The European Medicines Agency (EMA) issued regulatory recommendations and communications in 2021 about the risk of thrombosis with thrombocytopenia syndrome (TTS) associated with COVID-19 adenoviral vector vaccines Vaxzevria and Jcovden. Little is known about how such measures impacted on national vaccination strategies and how they influenced decision-making processes of policy-makers and experts. The aim of this study was to evaluate the impact of regulatory actions for Vaxzevria and Jcovden on national vaccination strategies following the EMA's 2021 review on safety measures on TTS. Methods: A grey literature review was performed to gather information on EMA's actions as well as changes to national vaccination strategies in Denmark, Greece, Latvia, the Netherlands, Portugal and Slovenia. Semi-structured interviews were held with experts who had either advisory or decision roles in national vaccination programmes to contextualise the results of the grey literature review and discuss their experiences. Interviews were coded and analysed on national levels. Results: EMA made various adaptations to product information and released safety warnings and other regulatory communications for both vaccines relating to TTS risk. Countries varied widely in changes made to national vaccination policies. Interviews revealed that experts relied mainly on their professional networks and information sources, other than the EMA, to inform their recommendations and/or decision-making. Conclusion: EMA's regulatory actions were not the main source informing adaptations to national vaccination strategies. National decision-makers country reverted to their preferred sources. The use of varying sources explains some of the variations in the vaccination strategies.