With several Covid-19 vaccines either being rolled out or under trial, here is a rundown of the various stages of their development.
On the market
The mRNA vaccine developed by US pharma giant Pfizer and German start-up BioNTech is already approved for use in the European Union, the United States, Canada, Britain and several other nations.
Clinical trials showed the vaccine, which delivers instructions to the body to help the immune system identify and destroy Covid-19 molecules, is more than 95% effective.
Another mRNA vaccine, with a 94.1% efficacy rate, has been approved for use in the EU, North America, Britain, and several other nations, including Israel and Singapore.
This viral vector vaccine is authorised for use in the EU, Britain and other countries such as India.
It was shown to be 60% effective in trials, but a relative lack of safety and efficacy data among older participants has led several countries to recommend against administering the vaccine to those over 65.
Russia's vaccine works in a similar way to the AstraZeneca/Oxford jab, but has a 91.6% efficacy according to trial results.
More than a dozen nations have authorised its use, including Belarus, Armenia, Iran, Algeria, Argentina, South Korea and Venezuela.
Its makers have begun the process of asking for approval from the European Medicines Agency. Hungary is the sole EU member state that has started administering doses.
Two vaccines developed in China use the traditional technique of injecting the deactivated virus in order to trigger an immune response.
As well as the United Arab Emirates, Hungary, Cambodia, Peru and Zimbabwe have all started administering the vaccine, which its makers say is 79% effective.
The other Chinese-developed vaccine uses a similar technique and is authorised for use in China, Chile, Brazil and Turkey. Others such as Ukraine and Uruguay have pre-ordered doses.
Its makers say it is 50%effective against Covid-19 (and 80%effective against severe illness), but trial results have not yet been made public.
This inactivated virus vaccine is used currently in India.
A Chinese-made viral vector vaccine was authorised for use in Mexico last week, but has not yet been administered to the public.
JOHNSON & JOHNSON
The US pharma giant has asked for emergency use authorisation for its single-shot vaccine in the US and EU.
South Africa notably announced this month that it would prioritise procuring the Johnson & Johnson vaccine over AstraZeneca's.
Trials showed it to be 66% effective against Covid-19 and up to 85%effective against serious forms of infection.
This American vaccine is under rolling review by the EMA, which has the ultimate say on EU medical authorisations.
It is based on "sub-unit" proteins that trigger an immune response without delivering the whole virus.
Its makers say it is 89.3% effective.
The German vaccine entered EMA review last week. It uses similar technology to the Moderna and Pfizer/BioNTech jabs.
Still in development
The World Health Organization says there are currently 69 vaccines against the novel coronavirus in human trials.
An additional 180 candidate vaccines are under development, but have yet to begin testing on humans.