A coronavirus vaccine being trialled by two pharmaceutical giants has been found to be more than 90% effective in preventing Covid-19 in tests. 

The vaccine is being developed by Pfizer and Germany’s BioNTech. 

The study of more than 43,500 people – which was held across six countries – did not uncover any serious safety concerns, the companies said. 

Meanwhile, just 94 people developed Covid-19 during the trial. 

To confirm the efficacy of the vaccine, Pfizer will continue the trial until there are 164 coronavirus cases among participants, the Reuters news agency reported. 

Pfizer is expected to ask the US for authorisation for emergency use of the vaccine by the end of November. 

No.10 said the UK had procured 40m doses of the vaccine, with 10m set to be manufactured by the end of the year if the jab is approved by regulators. Reports of a deal between the UK and Pfizer in July suggested 30m doses had been secured – it is not clear when the extra 10m were added.

Pfizer CEO Dr Albert Bourla said the development marked a “great day for science and humanity”. 

“The first set of results from our Phase 3 Covid-19 vaccine trial provides the initial evidence of our vaccine’s ability to prevent Covid-19,” he said.

“We are reaching this critical milestone in our vaccine development program at a time when the world needs it most with infection rates setting new records, hospitals nearing over-capacity and economies struggling to reopen.” 

Bourla said that scientists were “a significant step closer to providing people around the world with a much-needed breakthrough to help bring an end to this global health crisis”.

Pfizer and BioNTech said that, based on current projections, they expected to be able to produce 50m doses of the vaccine in 2020 and as many as 1.3bn in 2021.

Concerns have also been raised about the logistical challenges associated with the vaccine, with the BBC reporting that it needs to be kept in ultra-cold storage at below -80C, while the WSJ said it was around -70C.

What type of vaccine is this?

The jab is known as a messenger RNA (mRNA) vaccine.

Conventional vaccines are produced using weakened forms of the virus, but mRNAs use only the virus’s genetic code.

An mRNA vaccine is injected into the body where it enters cells and tells them to create antigens.

These antigens are recognised by the immune system and prepare it to fight coronavirus.