Covid vaccination campaigns are underway in the UK and across the world.
A range of vaccines is being used to reduce people's chances of getting sick, needing hospital treatment or dying.
Why do we need a vaccine?
It is more than a year since the virus first emerged, yet many people are still vulnerable.
The restrictions on our lives help keep the virus in check as they reduce opportunities for the virus to spread.
Vaccines teach our bodies to fight the infection and are "the" exit strategy from the pandemic.
The big three - Pfizer/BioNTech, Moderna and Oxford/AstraZeneca
The three vaccine frontrunners are those developed by Pfizer-BioNTech, Moderna and Oxford-AstraZeneca.
Pfizer and Moderna both developed RNA vaccines - a new approach that is incredibly quick to design.
They inject a tiny fragment of the virus's genetic code into the body, which starts producing part of the coronavirus and pushes the body to mount a defence.
These have been approved for use in the UK, Europe and the US.
The Oxford vaccine is subtly different as it uses a harmless virus to carry the same genetic material into the body. This has been approved in the UK and Europe.
It is the easiest of the three to use as it can be stored in a fridge, rather than needing very cold temperatures.
All three are supposed to be given in two doses.
Janssen and Novavax
A single-dose Covid vaccine made by Janssen has now been approved for use in the UK.
Twenty million doses of the jab, which was 85% effective in stopping severe illness from Covid-19 in trials, will arrive later this year.
Because only one dose is needed - and the vaccine can be stored in a fridge - it could have a significant impact around the world. A billion doses are planned this year.
Another jab, Novavax, is also being reviewed by drugs regulators.
It uses a different, old-school, approach to vaccines - proteins from the virus and a chemical to prime the immune system are injected into the body.