Mass vaccination campaigns are under way in the fight back against the coronavirus.
A range of vaccines, designed in completely different ways, are being used to reduce people's chances of getting sick, needing hospital treatment or dying.And two new vaccines have just been shown to work in large scale clinical trials.
Why do we need a vaccine?
It is more than a year since the virus first emerged, yet the vast majority of people are still vulnerable to the virus.
The restrictions on our lives are the only thing holding 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 threeThe three vaccine frontrunners are those developed by Pfizer/BioNTech, Moderna and Oxford/AstraZeneca.
Pfizer and Moderna have 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, this starts producing part of the coronavirus and the body to mounts 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, BBC reported.
All are supposed to be given as two doses, but the UK is prioritising giving as many people as possible the first dose and delaying the second.
What is the rest of the world doing?
There are other noteworthy vaccines even if they are not being used in Europe and the US.
The Sinovac, CanSino and Sinopharm vaccines have been developed by scientists in China and deals have signed with other countries in Asia and South America. Around one million people in China are reported to have been given the Sinopharm injection.
The Sputnik V vaccine, developed by Russia's Gamaleya Research Centre, has published early trial data saying it is effective and some people have been immunised.
What about variants?
New versions of the coronavirus are emerging in countries around the world.
The results were still good and clearly better than no vaccine at all, but they emphasise how coronavirus is a moving target.
What still needs to be done?
Huge-scale manufacturing to produce billions of doses and distribute them around the world
Research to find out how long protection lasts
Research to discover what effect vaccine have on the spread of the virus