Evidence suggesting an initial half dose of the vaccine being developed by drugs firm AstraZeneca and the University of Oxford is more effective than a full dose is counterintuitive, and even took the researchers by surprise.
Trials of the AstraZeneca Oxford vaccine were carried out around the world, including in the United Kingdom, the US, Japan, Russia, South Africa, Kenya and several Latin American countries.
The most likely scenario for COVID-19 vaccine candidates in the EU is a one-year conditional marketing authorisation (CMA), European Medicines Agency (EMA) sources have told EURACTIV.
The final analysis of the experiments conducted on the vaccine comes only a week after the initial results of the Pfizer/BioNTech vaccine, which showed that the vaccine is more than 90 percent effective.
It added that it would seek emergency-use listing from the World Health Organization to accelerate vaccine availability in low-income countries.
The Oxford University candidate is an adenovirus vaccine, which is a much more established technology that's already been in use for decades, and which involves genetically altering a weekend common cold virus and using that to trigger a person's own natural immune response.
Separately, AstraZeneca executive Pam Cheng told Reuters that 20 million doses of the vaccine are expected to be available in Britain by the end of the year, and 70 million are expected to be provided by late March.
Two different dosing regimens were used, which yielded different results. Mr Poonawalla's company has an agreement with the government to mass-manufacture doses of the Covid vaccine.
The vaccine can be transported under "normal refrigerated conditions" of 2-8C, AstraZeneca said.
The pair said that regimen n=8,895 showed 62% efficacy when given as two full doses at least one month apart.
He noted that the researchers found that if people were given half a dose followed by a full dose, instead of two full doses, the prevention rate rises to 90 percent.
"This vaccine's efficacy and safety confirm that it will be highly effective against COVID-19 and will have an immediate impact on this public health emergency, " Soriot said. AstraZeneca has pledged to "ensure broad and equitable access to the vaccine at no profit for the duration of the pandemic".
Just months ago, "the idea that by November we would have three vaccines, all of which have got high effectiveness ..."