Part of our monitoring role includes reviewing reports of suspected side effects. Any member of the public or health professional can submit suspected side effects through the Yellow Card scheme. The nature of Yellow Card reporting means that reported events are not always proven side effects. Some events may have happened anyway, regardless of vaccination. This is particularly the case when millions of people are vaccinated, and especially when most vaccines are being given to the most elderly people and people who have underlying illness.
https://www.gov.uk/government/publications/coronavirus-covid...
Pfizer: https://assets.publishing.service.gov.uk/government/uploads/...
AstraZeneca: https://assets.publishing.service.gov.uk/government/uploads/...
Disclaimer from UK.gov:
Part of our monitoring role includes reviewing reports of suspected side effects. Any member of the public or health professional can submit suspected side effects through the Yellow Card scheme. The nature of Yellow Card reporting means that reported events are not always proven side effects. Some events may have happened anyway, regardless of vaccination. This is particularly the case when millions of people are vaccinated, and especially when most vaccines are being given to the most elderly people and people who have underlying illness. https://www.gov.uk/government/publications/coronavirus-covid...
Edit: Added disclaimer from UK.gov