Pharmaceutical giant Pfizer and biotech firm BioNTech have said their coronavirus vaccine was more than 90% effective in preventing Covid-19 among those without evidence of prior infection.
The results are based on the first interim analysis of Phase 3 of the study, and evaluated 94 confirmed cases of Covid-19 in trial participants.
The study enrolled 43,538 participants, with 42% having diverse backgrounds, and no serious safety concerns have been observed, the companies report.
They add that safety and additional efficacy data continue to be collected.
The case split between vaccinated individuals and those who received the placebo indicates a vaccine efficacy rate above 90%, at seven days after the second dose.
Researchers say this means that protection is achieved 28 days after the initiation of the vaccination, which consists of two doses.
However, they caution that as the study continues the final vaccine efficacy percentage may vary.
Dr Albert Bourla, Pfizer chairman and chief executive, said: “Today is 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 added: “We will continue to collect further data as the trial continues to enrol for a final analysis planned when a total of 164 confirmed Covid-19 cases have accrued.
“I would like to thank everyone who has contributed to make this important achievement possible.”
The companies have planned to submit an application for emergency use authorisation to the US Food and Drug Administration (FDA) after the required safety milestone is achieved, which is currently expected to be in the third week of November.
The clinical trial will continue through to final analysis at 164 confirmed cases in order to collect further data and characterise the vaccine candidate’s performance against other study endpoints.
Professor Ugur Sahin, BioNTech co-founder and chief executive, said: “The first interim analysis of our global Phase 3 study provides evidence that a vaccine may effectively prevent Covid-19.
“This is a victory for innovation, science and a global collaborative effort.”
The UK has secured 40 million doses of the Pfizer/BioNTech vaccine called BNT162b2 – the first agreement the firms signed with any government.
It is thought people will need two doses, meaning not enough shots have been secured for the entire UK population.
As well as the efficacy data generated from the clinical trial, Pfizer and BioNTech are working to prepare the necessary safety and manufacturing data to submit to the FDA to demonstrate the safety and quality of the vaccine product produced.
They currently expect to be able to produce up to 50 million vaccine doses globally in 2020 and up to 1.3 billion doses in 2021.
The data from the full Phase 3 trial will be submitted for scientific peer-review publication.
Azra Ghani, professor in infectious disease epidemiology at Imperial College London, said: “These new results represent the first demonstration of substantial efficacy of a vaccine candidate against Covid-19 disease which is very welcome news.
“It is important to bear in mind that these are early results based on a relatively small number of cases.
“In addition, the efficacy estimate is based on seven days of follow-up of participants following the second dose – further data in the coming weeks and months will provide a better picture of longer-term vaccine efficacy.”