Developing a COVID-19 vaccine in record time is a global priority.
That work is under way, as Britain's Prince William saw for himself this week.
He visited the Oxford-based scientists who are working on a vaccine with AstraZeneca.
It's already in human trials.
PRINCE WILLIAM: "A very willing guinea pig"TRIAL PARTICIPANT: "Apparently yeah."3. (SOUNDBITE) (English) ANDREW POLLARD AND PRINCE WILLIAM SPEAKING TO VACCINE TRIAL PARTICIPANT, SAYING:POLLARD: "I know it's incredibly important that volunteers do help with these trials because we can't have the vaccine without people willing to take part. It's critical."
Finding human participants is one thing.
But producing enough vaccines to end the pandemic will be the biggest medical manufacturing feat in history.
From deploying experts amid global travel restrictions, to managing extreme storage conditions....
Even inventing new kinds of vials and syringes for billions of doses.
Any hitch in an untested supply chain - could harm the complex process.
Experts say companies usually have years to figure these things out, but now only have weeks.
Companies are racing to scale up machinery to address a critical shortage in automated finishing and filling capacity.
That's the final step of putting the vaccine into vials or syringes, sealing them and packaging them up for shipping.
Some companies are having to work out how to produce vials that won't shatter at the super-cold temperatures.
Travel restrictions are also causing havoc.
Johnson & Johnson, which plans to start clinical trials this summer, has struggled to send its vaccine experts to oversee the launch of production sites.
By setting up massive clinical trials involving 10,000 to 30,000 volunteers per vaccine, scientists hope to get an answer on whether a vaccine works as early as this October.
But even if they succeed, manufacturing in bulk, getting regulators to sign off and packaging billions of doses will likely be a monumental challenge.