The world may be one step closer to getting a coronavirus jab after Oxford University's vaccine candidate entered its final stage of tests in the US.
UK drug giant AstraZeneca, which owns the rights to the vaccine, said it had enrolled 30,000 American volunteers to take part in its phase three clinical trial.
It now means 50,000 people worldwide are taking part in studies to see whether the jab - known as AZD1222 - can actually prevent people getting infected with Covid-19.
Thousands of volunteers have already been injected with the experimental drug in the UK, Brazil and South Africa and are being monitored by scientists.
Oxford's Professor Sarah Gilbert, the brains behind the jab, said preliminary data from trials in these countries could be expected in the coming weeks.
Cambridge-based AstraZeneca said further trials are planned in Japan, where there has been a deadly second wave, and Russia, where there have been a million cases.
AstraZeneca and Oxford scientists have repeatedly promised to deliver the vaccine to the most vulnerable groups to Covid-19 by the end of the year.
Meanwhile, the British drugmaker today struck a £15million deal with Oxford Biomedica to mass-produce the vaccine if it is proven to be effective.
Gene and cell therapy firm Oxford Biomedica will be the sole manufacturer of the vaccine in Britain for 18 months.
AstraZeneca has also struck deals with manufacturers in China, the US, and across Europe as it looks to supply the entire world with the Oxford jab.
Nobel Prize-winning scientists are among 100 experts calling for healthy people to be infected with coronavirus in a bid to speed up the development of vaccines (file)
Oxford Biomedica says it will receive £15m as a capacity reservation fee, plus as much as £35m to make multiple large-scale batches of the vaccine if it works.
Early trials have shown promising results, with tests showing the vaccine is safe to use in humans and appears to provoke an immune response. But data that proves it protects people is not expected until later this year.
To prove without doubt they protects people from infection, vaccines need to go through rigorous phase three trials.
The UK is the host of research and development efforts of the vaccine, which has been developed by researchers in Oxford and will be manufactured by AstraZeneca, a company based in Cambridge.
The British Government has ordered 100million doses of the jab and has already started manufacturing them so they're ready to go if and when clinical trials are successful. The price paid has not been disclosed.
The US Government has ordered 100million doses of the vaccine and contributed $1.2billion (£910m) to the research and development of the jab.
European Union (EU)
The European Commission has agreed a deal for 300million doses of the vaccine if its clinical trials work, with the option to buy a further 100million. The deal has been made on behalf of countries in the EU. The amount of money spent is unknown.
Australia has confirmed it ordered enough doses of the vaccine to give one to its entire population of 25million people. It is not clear how many doses the nation has ordered. The UK - with a population of 66m but an order of 100m - ordered more than it needs.
One company in China has agreed a deal with AstraZeneca to make at least 100million doses of the vaccine.
Shenzhen Kangtai Biological Products, based in the city of Shenzhen, will increase capacity to 200m per year by the end of 2021.
A Russian company, R-Pharm, also has a deal to produce and distribute the vaccine, but it is unclear how many it will make or what it will pay to AstraZeneca.
Brazilian officials have set aside $360million (£274m) for at least 100million doses of the vaccine. Brazil is currently in one of the worst Covid-19 crises in the world with more than 3.6million official cases so far and 114,000 deaths.
In these tests the vaccine is being given to tens of thousands of people in real-world environments to see if it stops them from catching Covid-19 in the community.sonos sonos One (Gen 2) - Voice Controlled Smart Speaker with Amazon Alexa Built-in - Black read more
The Oxford scientists behind the jab had to move their