Coronavirus: How will the world vaccinate seven billion?

Teams across the world are working to develop a vaccine that will be effective against Covid-19.

Prime Minister Boris Johnson has called it "the most urgent shared endeavour of our lifetimes".

But away from the high-tech science of finding a winning formula, what about the logistics of rolling out a vaccine to seven billion people worldwide?

In the UK, the heart of that effort is at the Harwell Science Campus, on an ex-RAF airbase in Oxfordshire.

It is going to be the UK's Vaccines Manufacturing and Innovation Centre (VMIC), plans for which have been brought forward by Covid-19.

"We've really compressed the timeline into almost half. So whereas we were expecting to have it ready at the end of 2022, we're now hoping to have it online in 2021," explains Matthew Duchars, chief executive of VMIC.

Mr Duchars is yet to take a summer holiday because he knows that this place could end up producing the Oxford University vaccine. He's in constant touch with the team at the Jenner Institute, just down the road in Oxford.

He says it's a heavy responsibility.

"It's critically important, not just for the country but globally, to be able to produce these types of vaccines quickly and effectively," he says.

"To use an analogy - it's like baking a cake at home. You can spend hours preparing the perfect cake and now you've got to go out and bake 70 million of them and they all have to be perfect, so it's quite a challenge."

That's putting it mildly.

Oxford University has already had to secure enough temporary lab space to start manufacturing its vaccine now, even before it knows the results of its global trials.

Ultimately, the human race will need to make billions of doses of several types of Covid-19 vaccines. They will all have to be manufactured, distributed and administered across the globe.

The international vaccines alliance - Gavi - is urging countries to start thinking about vaccine rollout now.

But it's not easy to get international co-operation, because many rich countries are already doing bilateral deals with drug companies to make sure they can secure supplies if the magic formula is found.

Seth Berkley, Gavi's CEO, says one of the biggest hurdles he's facing is so-called "vaccine nationalism".

"I think we need all countries to be thinking about this in a globally minded way, partially because it's the right thing to do but also because it's a self-interest issue," he says.

"If you have large reservoirs of virus circulating in surrounding countries, you can't go back to your normal trade, travel or movement of people. It's really important to have that mindset: we're not safe, unless everybody is safe."

As well as trying to make sure developing countries get access to the right vaccines, Mr Berkley has to think about the more prosaic aspects of vaccine roll-out, including whether or not there are enough glass vials in the world. There have been reports of a potential bottleneck in medical glass production.

"We were worried about that," Mr Berkley admits, "so we went ahead and purchased enough vials for two billion doses, that's the number of doses we hope to have ready by the end of 2021."

If glass vials are a potential problem, then so are fridges, since most vaccines need to be kept at low temperatures.

Prof Toby Peters, an expert in cold chain logistics at Birmingham University, is helping organisations like Gavi think about how they can maximise existing refrigeration capacity in developing countries.

He says: "It's not just a vaccine fridge, it's actually all the other pieces too: the pallets which move it in the planes; the vehicles that move it to the local stores, and then the motorbikes and the people who take it out right into the communities. All these have to work seamlessly."

Prof Peters has been talking to global food and drink companies to explore borrowing cold chain storage to help with this mammoth project.

To make the vaccine roll-out more manageable, countries will have to work out who to prioritise in their populations.

Dr Charlie Weller, head of vaccines at the UK's Wellcome Trust, says countries are going to have to ask some frank questions.

"Who needs this vaccine? Which are the highest risk groups? And who are the highest priority? Because what we're pretty clear about is any initial vaccine is likely to outstrip supply, so choices will need to be made."

Even doing the actual vaccinations will be tricky.

The UK, for example, is looking at a template which uses its network of polling stations as a way to process the population. But for poorer countries it's even more daunting.

Dr Weller insists strong healthcare systems will be key, with healthcare workers who have the right technical skills to immunise the target groups.

The scientists all think some kind of vaccine will be found. But many of them say they are kept awake at night by the sheer scale of what needs to be done to get it to billions of people.