It is just over nine months since Chinese scientists posted the genetic sequence of the new coronavirus online, and the very next day – even though it was a Saturday – researchers began using the data to design vaccines.

That was the starting gun for what has become a global effort to create a vaccine.

“I cannot think of any pathogen which has attracted the amount of interest that Covid-19 has over the past nine months,” said Paul Fine, a professor of communicable disease at the London School of Hygiene and Tropical Medicine.

“Let’s hope we get a vaccine and let’s hope it’s highly effective. Let’s hope its relatively cheap. Let’s hope it’s safe. Let’s hope it can be produced in large enough quantities.”

Let’s hope its cheap. Let’s hope it’s safe. Let’s hope it can be produced in large enough quantities

Paul Fine, London School of Hygiene and Tropical Medicine.

There are no fewer than 193 vaccines under test, 10 of which are in late-stage clinical trials where thousands of volunteers are monitored for side effects and immunity.

While many people have already been vaccinated against the coronavirus, this has primarily happened as part of clinical trials and no vaccine has completed the full testing and regulatory processes for more widespread use.

In August, Russia approved the vaccine developed by its Gamaleya research institute in Moscow, but it remains in phase 3 clinical trials. It was recently announced that some of these trials would happen in the UAE.

When will vaccination begin?

Vaccines must be approved by regulators before immunisation can begin. Approvals depend on the results of clinical trials, some of which are likely to report results in the coming months or even weeks.

Among the front-runners likely to unveil data within the next month or so are Russia’s Sputnik V vaccine and the vaccine developed by the University of Oxford and AstraZeneca.

Some reports suggest it is unlikely that mass vaccination programmes will begin before the middle of next year, but others forecast they could start within months.

“I cannot tell you when it will be. It will be when they have shown efficacy and safety,” said Prof David Salisbury, an associate fellow at London think tank Chatham House.

“The regulators have said they will accept anything [with an efficacy] above 50 per cent. They will have to show data on safety.”

Despite political pressure from the United States president, Donald Trump, regulators in the US are unlikely to give authorisation before the election next month.

Developed nations have plans for mass vaccination centres and mobile units, with some reports indicating that younger people, who are less at risk from the coronavirus, may be left out of certain vaccination programmes.

Prof David Taylor, professor emeritus of pharmaceutical and public health policy at University College London, said vaccine development appeared to have gone “as well as we could have hoped”.

“I would not be surprised if we had a licensed vaccine by the end of the year or first month or two of next year, and wouldn’t be surprised if that started to be rolled out in the second quarter of next year,” he said.

“I would hope that this time next year we would have vaccination as a significant part of control.”

Bill Gates, whose foundation has signed agreements with more than a dozen drug makers to speed up vaccination trials, has suggested that wealthy countries could return to something close to normal life by the end of next year.

How long will vaccination take?

The Coalition for Epidemic Preparedness Innovation (CEPI), which is backed by several governments and the Bill and Melinda Gates Foundation, surveyed the industry and found there is total global manufacturing capacity for as many as four billion coronavirus vaccine doses a year.

“If we work with a two-dose model with both doses having the same amount of vaccine, that would mean two billion people could receive a vaccination and go through the entire vaccination schedule,” said Dr Cleo Kontoravdi, a reader in biosystems engineering at Imperial College London and who is part of a research group that has modelled coronavirus vaccination programmes.

Manufacturing has already begun, which should reduce the extent to which production capacity will act as a bottleneck when widespread vaccination gets the green light.

“What we don’t know is the extent of stockpiling and at which locations these exist. This is the reason we cannot give definitive estimates on time lags,” said Dr Kontoravdi.

She said numerous factors, other than manufacturing capacity, could delay vaccination programmes.

“The aviation industry has calculated it will take 1,000 jumbo jets per billion doses. Transport at the temperature required is going to be another time-limiting step,” she said.

“The last time-limiting step, we believe, will be administering – giving the vaccine to people around the world – including in places that are possibly rural, and giving it in a way that’s in line with social distancing and so on.”

Overall, it remains difficult to estimate how long vaccination programmes will take, according to Dr Kontoravdi, but she said delays were likely to be measured in months rather than weeks.

Will poorer countries be shut out?

The degree to which developing countries will gain access to vaccines remains in question, not least because many governments in wealthier nations have “pre-ordered” as many as two billion doses after pumping hundreds of millions of dollars into vaccine research.

“Let’s hope that it’s not just a few rich countries getting all the vaccine and the rest of the world without. I think that would be abominable. There’s an issue here of global justice,” said Prof Fine.

Others have suggested that, because developed nations tend to have older populations, it may be appropriate if they are able to access supplies first.

“The evidence is we will have effective worldwide distribution because of the worldwide system in place and the underlying social responsibility,” said Prof Taylor.

Will the vaccines that are administered change over time?

There are 10 vaccines currently in phase 3 clinical trials, 32 in earlier stages of clinical analysis, and 151 in preclinical evaluation, according to the World Health Organisation.

Not all of these will complete trials and be approved for use, but new vaccines, particularly those that have taken longer to develop because they are not based on tried-and-tested technology, are likely to come on stream after the first wave of vaccines.

Analysts therefore suggest the vaccines used may change over time, with more effective ones approved later on potentially replacing those given the go-ahead initially.

“It’s likely the efficacy may not be as high as we want in this first-generation vaccine,” said Dr Kontoravdi. “All the teams are already working on second-generation vaccines likely to be more efficacious … Right now we’re going to be doing the best we can in protecting the most vulnerable.”

Clinical trials have not been without difficulties. The University of Oxford / AstraZeneca clinical trials were paused globally because a volunteer in the UK fell ill, although the work has restarted everywhere except the US.

This week, two US clinical trials were paused over safety concerns. On Tuesday, US pharmaceutical firm Eli Lilly suspended Phase 3 trials of its lab-produced antibody treatment in hospitalised patients over an unspecified incident.

A day earlier, American pharmaceutical giant Johnson & Johnson temporarily halted its Phase 3 Covid-19 vaccine trial due to an unexplained illness in a study participant.

Such pauses for safety reasons are not unusual in large-scale clinical trials and do not necessarily indicate that a medicine is hazardous.