• The Oxford-AstraZeneca vaccine is one of several seeking to secure approval from medicine regulators, amid rising hopes that a mass vaccination campaign could help to bring an end to the coronavirus pandemic.
• The vaccine has a "distinct comparative advantage" over other leading candidates, according to Richard Horton, editor-in-chief of The Lancet medical journal.

LONDON — The Oxford-AstraZeneca coronavirus vaccine has a "distinct comparative advantage" over other leading candidates, the editor-in-chief of The Lancet medical journal said Wednesday.

The comments by Dr. Richard Horton came a day after his peer-reviewed journal published a study that found the vaccine candidate was safe and effective.

The data also suggested that the vaccine can help reduce the spread of Covid-19, as well as preventing illness and death.

The vaccine, produced in a collaboration between the University of Oxford and the British pharmaceutical giant, is one of several seeking to secure approval from medicine regulators amid rising hopes that a mass vaccination campaign could help end the pandemic, which has killed more than 1.55 million people worldwide.

"The Oxford AstraZeneca vaccine is the vaccine right now that is going to be able to immunize the planet more effectively, more rapidly than any other vaccine we have," Horton told CNBC's "Street Signs Europe."

Horton said it is important to think about vaccine immunization on a global scale "because even if we immunize one country, the threat then is you reintroduce the virus from another country that is not protected."

"That means that you need a vaccine that can get to lower middle-income countries," Horton said. He added it was "not practicable" to launch a global vaccination campaign with storage needs of minus 70 degrees Celsius (minus 94 degrees Fahrenheit), apparently referring to the Pfizer-BioNTech vaccine.

The Oxford-AstraZeneca vaccine can be stored at regular refrigerator temperature. It is also cheaper than its peers, thought to cost around $4 per dose.

Pfizer-BioNTech is reportedly charging around $20 per dose for its coronavirus vaccine. Moderna has said it is charging $32 to $37 per dose, and Johnson & Johnson has said its candidate will cost around $10 per dose.

"So that is why I think over the next few weeks we need to be looking for the approval, the emergency authorization of this vaccine, and then we need to get manufacturing scaled up to immunize the world," Horton said.

'$100 million question'

The U.K. on Tuesday rolled out the first coronavirus vaccines to the public, with 90-year-old Margaret Keenan making history as the world's first person to receive the Pfizer-BioNTech vaccine outside of trial conditions. The vaccine was approved by the U.K. drug regulator last week.

The Oxford-AstraZeneca vaccine has yet to be approved by regulatory authorities around the world. The Medicines and Healthcare products Regulatory Agency, the U.K. medicine regulator, said Wednesday it would assess the dosing regimens of the Oxford-AstraZeneca vaccine.

The Lancet study found the vaccine had an effectiveness of 62% for trial participants given two full doses, but 90% for a subgroup given half a dose followed by a full dose.

When asked why the Oxford-AstraZeneca vaccine had been found to be 90% effective with this dosing regimen, Horton replied: "Well, that's the $100 million question."

"This was unplanned, it was unexpected, but it might be a very important serendipitous finding. It is possible, and this is perhaps the most likely explanation, that by giving a low dose of the vaccine early on, the body doesn't mount an immune response against the vector because this is a virus vector delivered vaccine."

AstraZeneca's vaccine is a viral vector inoculation that is based on a weakened version of a common cold virus that causes infections in chimpanzees. It is designed to prime the immune system to attack the coronavirus, known as SARS-CoV-2, if it later infects the body.

"And so, when you give the second dose, the body isn't reacting as strongly against that vector and therefore the vaccine is more efficacious in protecting against Covid-19," Horton said.

He added that another clinical trial would be required to better understand the surprising finding.

"The data they have delivered shows this drug is highly effective, although not as effective as we see for the two mRNA vaccines," Andrew Baum, global head of health care at Citi, told CNBC on Tuesday.

Unlike Oxford-AstraZeneca's vaccine, Pfizer-BioNTech and Moderna use messenger RNA, or mRNA, technology. It's a new approach to vaccines that uses genetic material to provoke an immune response.

"Is it as clean as the Pfizer and the Moderna data? No. But I think it has an incredibly important role not only in Western European markets, but I think especially in the less-developed world," Baum said, referring to the Oxford-AstraZeneca vaccine.

The cost, ease of manufacture and the absence of a need for special cold storage will mean "this is really the only vaccine that is going to suppress or even eradicate SARS-CoV-2, the virus that causes Covid-19, in the many millions of individuals in the developing world," Baum said.

— CNBC's Holly Ellyatt contributed to this report.