A dispute broke out in January 2021 between the European Commission and the pharmaceutical company AstraZeneca AB about the provision of COVID-19 vaccines during the COVID-19 pandemic, and, in February, spilled out into a dispute over Article 16 of the Northern Ireland Protocol. Vaccination proceeded apace in the UK but more slowly in the EU, and by the end of March 2021, over 30% of the UK population had received at least one dose of vaccine compared to about 8% of the EU population. This was partly due to limited availability of the AstraZeneca vaccine in the EU. The World Health Organization and the European Medicines Agency continued to state that the vaccine was safe and effective. However, a representative of the European Medicines Agency said in June that vaccines based on the mRNA technology should be preferred if available for all age groups, including for the over 60s.

Arlene Isobel Foster, Baroness Foster of Aghadrumsee,, is a British broadcaster and politician from Northern Ireland who served as First Minister of Northern Ireland from 2016 to 2017 and 2020 to 2021 and leader of the Democratic Unionist Party (DUP) from 2015 to 2021. Foster was the first woman to hold either position. She is a Member of the House of Lords, having previously been a Member of the Legislative Assembly (MLA) for Fermanagh and South Tyrone from 2003 to 2021.