The three Covid-19 vaccines are from Pfizer-BioNTech, the University of Oxford and Astra-Zeneca and Moderna.
The Pfizer, Oxford and Moderna vaccines each require two doses and you are not fully vaccinated until a week after your second shot.
But there are many differences between them.
BBC health correspondent Laura Foster looks at how much immunity they give, how they prevent infection and which one is better.
Video by Mel Lou, Laura Foster, Terry Saunders and Mattea Bubalo