You will be given a booster dose of either the Pfizer or Moderna vaccine, though in some cases AstraZeneca may be an option if this is the vaccine you had for the first two doses.
There are four common side effects, which are the same for all COVID-19 vaccines used in the UK.
They include having a painful, heavy feeling and tenderness in the arm where you had your injection. This tends to be worse around one to two days after the vaccine.
Some people will also feel tired, have a headache, or experience general aches, or mild flu like symptoms.