If or when scientists succeed in making a coronavirus vaccine, there won’t be enough to go around.
Research labs and pharmaceutical companies are rewriting the rulebook on the time it takes to develop, test and manufacture an effective vaccine.
Unprecedented steps are being taken to ensure roll-out of the vaccine is global. But there are concerns that the race to get one will be won by the richest countries, at the expense of the most vulnerable.
So who will get it first, how much will it cost and, in a global crisis, how do we make sure nobody gets left behind?
Vaccines to fight infectious diseases usually take years to develop, test and deliver. Even then, their success is not guaranteed.
To date, only one human infectious disease has been totally eradicated – smallpox – and that took 200 years.
The rest – from polio to tetanus, measles, mumps and TB – we live with, or without, thanks to vaccinations.